text:
\section{Introduction}

Although solar physics is one of the most mature branches of
astrophysics, the Sun confronts us with a large number of outstanding
problems that are fundamental in nature.  These problems include the
determination of the structure and dynamics of the solar atmosphere,
the magnetic field evolution in the chromosphere and corona, coronal
heating, the physics of impulsive energy release, energetic particle
acceleration and transport, the physics of coronal mass ejections
(CMEs) and shocks, as well as the solar origin of space weather
drivers.

Solar radio astronomy has already provided important insights into
these problems because (i) two of the natural frequencies of the solar
magnetized plasma, the electron plasma frequency, $\nu_{pe}$, and the
electron gyrofrequency, $\nu_{ce}$, fall into the radio band, and (ii)
radio emission is sensitive not only to the properties of radiating
electrons but also to the properties of the ambient plasma and magnetic field.
However, the full exploitation of the diagnostic potential of solar
radio emission is instrumentally demanding because solar radio sources
can be both small
\citep[$\lesssim$ 1$\arcsec$ in localized episodes of energy  release; e.g.
see the VLBI observations by][]{Tapping83}
and large
\citep[$\gtrsim$ 1$\degr$ in radio CMEs; e.g.][]{Bastian01}, weak
($<1$~sfu in the quiet Sun) and strong ($>$ 10$^5$~sfu in large
flares). Furthermore flux variations down to msec time scales and
narrow-band features of relative bandwidth down to 1-0.01\% are often
observed in coherent flare/CME-related bursts.  Therefore,
non-incremental progress in solar radio astronomy requires
high-cadence, high-sensitivity, large dynamic range,  snapshot imaging
interferometric observations over a large bandwidth with adequate
$u-v$ coverage and angular and frequency resolution.  Unfortunately,
there has been no radio instrument that is capable of meeting all of
the above requirements.

Historically, solar radio observations have been performed along two
lines: spectroscopy and imaging observations.
Spectroscopic observations (primarily at decimeter, meter, and
decameter wavelengths) provide spatially unresolved data with time and
frequency  resolution of about $\lesssim$ 1 s and $\lesssim$ 1 MHz,
respectively, while  interferometric imaging observations take place
at discrete frequencies providing data with angular resolution from a
few arcsec to a few arcmin depending on the frequency of
observations.

During the last couple of decades, old solar-dedicated and
general-purpose radio
interferometers have been upgraded and some of them are now
capable of performing
solar radio spectroscopic imaging and the same is/will be true for new
instruments (either already deployed or under construction).
The solar-dedicated instruments include the upgraded
Expanded Owens Valley Solar Array \citep[EOVSA; see][]{Gary12}, the
Mingantu Ultrawide Spectral Radioheliograph \citep[MUSER;
see][]{Yan16}, the Nan\c{c}ay Radioheliograph
\citep[NRH; see][]{Kerdraon97}, the Nobeyama Radioheliograph
\citep[NoRH; see][]{Nakajima94}, and the upgraded Siberian Radioheliograph
\citep[Siberian RH; see][]{Lesovoi14} while the general-purpose
instruments include the expanded Karl G. Jansky Very Large  Array
\citep[VLA; see][]{Perley11}, the Low Frequency Array \citep[LOFAR,
e.g.][]{2013A&A...556A...2V}, the Murchison  Widefield Array \citep[MWA,
see][]{Tingay13,Bowman13}, the Long Wavelength Array
\citep[LWA; see][]{Ellingson09}, and the Giant Metre-wave Radio Telescope
\citep[GMRT; see][]{Swarup91}. A summary  of the specifications of
these instruments (in alphabetical order) is given in Table 1.

\begin{table}
\centering
\begin{threeparttable}
\caption{Instruments capable of performing solar radio spectroscopic imaging}
\begin{tabular}{llllll}
\hline
Instrument & Frequency & Spectral &  Time   & Angular & Solar \\
           & Range     & Resolution & Resolution  & Resolution & dedicated \\
           & (GHz)       & (MHz) & (msec)             & (\arcsec) &  \\
\hline
EOVSA       & 1-18           & 50                   & 20         & 3-57 & Yes \\
GMRT        & 0.15-1.50  & 0.05  & 100 & 2-20 & No \\
LOFAR       & 0.03-0.24   & 0.1         & 10  & 60-540  & No \\
LWA         & 0.02-0.08    & 0.008        & 1    & 2-8\tnote{a} & No \\
MUSER       & 0.4-15         & 25                 & 25-200     & 1.3-50 & Yes \\
NoRH  & 17, 34      & 1700      & 100  & 6-12  & Yes \\
NRH & 0.15-0.45   & 23-48     & 250  & 18-240 & Yes \\
MWA         & 0.08-0.30   & 0.04      & 500  & 16-60 & No \\
Siberian RH & 4-8            & 10                   & 560  & 15-30 & Yes \\
VLA         & 1-50       &   1         & 100 & 1-35 & No \\
\hline
\end{tabular}
\begin{tablenotes}
\item[a]{Currently only two LWA stations have been deployed; the angular
resolution cited here refers to the originally envisaged array.}
\end{tablenotes}
\label{table1}
\end{threeparttable}
\end{table}

The Square Kilometre Array (SKA) will be a general-purpose radio
instrument  whose construction is expected to start in 2020 and whose
characteristics will significantly exceed the capabilities of the instruments
of Table 1.  It will be capable of
performing solar  observations which will have the potential to
transform solar radio astronomy in particular, and solar physics in
general. A testament to this argument is the important results that
have come out of data obtained with SKA's ``precusor'' and ``pathfinder''
projects: the
LOFAR \citep[e.g][]{Morosan14,Morosan15,Morosan17,Reid17,Kontar17,2018ApJ...856...73C},
the MWA \citep[e.g.][]{Oberoi11,Mohan17,McCauley17,Suresh17,Cairns18,Sharma18},
the VLA \citep[][]{2009IAUS..257..529S,Chen13,2014ApJ...784...68K,Chen15},
and the LWA \citep[][]{Tun15}.

This paper is organized as follows.   In Section 2, we outline the
major features of the SKA and in Section 3 we discuss the
particulars of solar observations with it.  In Section 4 we
briefly outline solar radio emission mechanisms, and in Sections 5-9
we discuss open issues on solar radio astronomy and how the relevant
SKA observations can bring results of transformative nature. In
Section 10 we outline possible synergies between the SKA and other
instruments, and in Section 11 we summarize the paper.  Note that in
this paper we restrict ourselves only to the discussion of solar
physics problems that could be addressed by SKA observations; a discussion
of heliospheric physics problems which will be addressed by the SKA
lies outside the scope of this paper. A broader but shorter review discussing
SKA's potential impact on both solar and heliospheric physics is available
in \citet{Nakariakov15}.

\section{Overview of the instrument}

\subsection{Basic features}

This section is based on information from various documents that can
be found at \url{https://astronomers.skatelescope.org}.  The SKA is an
international project to build the world's largest and most sensitive
radio telescope. When completed the collecting area of the instrument
will be about one square kilometer, hence its name. The instrument
will be built in two phases, known as SKA1 and SKA2.  SKA1 will
correspond to about 10\% of the final collecting area and its
deployment will start in 2020 while commissioning activities are
expected to start in 2024. SKA2 will correspond to the full final
system and its construction will start,
subject to the performance of SKA1, after 2030.

The SKA1 will consist of two arrays, SKA1-LOW and SKA1-MID, that will
be built in Australia and South Africa, respectively.  The expected
configuration  of the two arrays is presented in the geophysical maps
of Figure \ref{fig1}.  The maximum baselines of the arrays is expected
to be about 65 km for SKA1-LOW and about 150 km for SKA1-MID.

\begin{figure}
\centering
\includegraphics[scale=0.5]{fig1a.eps}
\caption{Geophysical maps with the SKA1-MID (left) and SKA1-LOW (right)
configurations. The horizontal lines at the bottom left corners of the
maps correspond to 40/20 km (left/right map). Image credit: SKAO.}
\label{fig1}
\end{figure}

The SKA1-LOW will observe from $\sim$50 to 350 MHz and it will be
deployed in the Murchison desert of Western Australia (central
coordinate 26$\degr$ 41$\arcmin$ 49$\arcsec$S 116$\degr$ 37$\arcmin$
53$\arcsec$E) in the same region as the Australian SKA Pathfinder
(ASKAP)  and MWA arrays.  It will include about 131000 simple antennas
(e.g. log-periodic dual-polarization dipole elements) that are
arranged in 100-m-diameter stations  each hosting 90 elements.  In
each station the signal of all elements will be  added together
electronically, in phase, allowing the formation of an ``aperture
array'' (see Figure~\ref{fig2}, left).  The separation
between stations will increase from the central part of the array
toward its outer edge, reaching several kilometers there.

The SKA1-MID will observe in the range from 350 MHz to 15.3 GHz which
will be divided into three frequency bands (Band 1: 0.35-1.05
GHz, Band 2: 0.95-1.76 GHz, and Band 5: 4.60-15.30
 GHz). The array will include 133 15-m-diameter dishes (see
Figure~\ref{fig2}, right) and will also incorporate the 64
13.5-m-diameter  dishes of the MeerKAT array. SKA1-MID will be
deployed in the Karoo desert of South Africa, ~500 km north of Cape
Town (central coordinate 30$\degr$ 43$\arcmin$ 16$\arcsec$S 21$\degr$
24$\arcmin$ 40$\arcsec$E). The dishes will be placed along a
three-armed spiral (see Figure~\ref{fig1}, left); along each arm the
separation of dishes will increase with the  distance from the center
of the array.

\begin{figure}[h]
\centering
\includegraphics[width=\textwidth]{fig2.eps}
\caption{Artist's impression of the SKA1-LOW aperture arrays (left)
and SKA1-MID dishes (right). Image credit: SKAO.}
\label{fig2}
\end{figure}

\begin{table}
\caption{Summary of SKA1 specifications}
\begin{tabular}{lll}
\hline
Parameter & SKA1-LOW value  & SKA1-MID value \\
\hline
Frequency range (MHz)   & 50-350 & 350-15300   \\
Angular resolution ($\arcsec$) & 4-24 &  0.025-1 \\
Time resolution (s) & 0.001-9 & 0.001-9 \\
Frequency resolution (kHz) & 5 & 15-76 \\
Field of view (deg$^2$) & 2-39 &  $\leq$ 1.4  \\
Largest angular structure ($\arcmin$) & 60-500 & 15-80  \\
Sensitivity ($\times 10^{-3}$ sfu) & 0.46-4.00  & 0.16-0.90  \\
\hline
\end{tabular}
\label{table2}
\end{table}

In Table 2 we present a summary  of SKA1's specifications. They
represent an unprecedented improvement over all existing
radio telescopes and will allow SKA1 to contribute to decisive
advances in practically all branches of modern astrophysics
\citep[e.g. see][and references therein]{Braun15}.

The SKA2 detailed specifications will be finalized depending on the
progress of SKA1. It is anticipated that both the SKA2-LOW
and -MID arrays  will form five 300-km-long spirals. There are plans
for the deployment of a few extra dishes to southern and central
African states (i.e. away from the instrument's core spiral configuration)
that will yield maximum baseline of about 3000 km.

The development of an instrument of such size poses difficult
construction and engineering problems. Furthermore, even the SKA1 will
produce data rates of several TB/s whose processing will require
central supercomputers capable of in excess of 100 petaflops
(i.e. 10$^{17}$ floating point operations per second) of  raw
processing power. The technical consortia  that are responsible to
build the SKA rely on the  recent huge progress both in the design of
antennas and wide-bandwidth feeds and in the transport and process of
large amounts of data. These recent developments have resulted in the
development of instruments (either new or upgraded old ones) that are
engaged in SKA-related technology and science  studies. These
instruments are called ``SKA precursors'' (if located at future SKA sites,
e.g. the MWA) or ``SKA pathfinders'', the latter include the VLA, the
LOFAR, the GMRT and others (for a complete census, see
\url{https://tinyurl.com/yaageuhz}).

\subsection{Modes of observations and data analysis}

SKA is an evolving project and several of its engineering, hardware
and software aspects have not been finalized yet. The technical aspects of
the SKA project (including software) are outlined in \citet{Hall05} while
more up-to-date information can be found at
\url{https://astronomers.skatelescope.org}.

The signals collected from MID and LOW arrays will be digitized
and fed into the instument's
``Central Signal Processor'' (CSP)\footnote{For more details see
 \url{https://www.skatelescope.org/csp}.}. CSP's main task will be
the collection, correlation, filtering, and analysis of the
observational data, according to the requirements of each observing
run.  To meet the requirements imposed by the SKA's specifications,
the CSP will utilize extremely fast computers (see Section
2.1). Furthermore, to reduce power consumption, most of the signal
processing will be done in Field-Programmable Gate Arrays (FPGAs) and
Gaphics Processing Units (GPUs).

Telescope resources will be enhanced by allowing users of both
telescopes (MID and LOW) to divide  collecting area into up to 16
subarrays and operate each subarray as an independent
instrument. Users will be allowed to schedule their observing run,
select observing mode, and determine the timeline of their
observations for each subarray independently.

The SKA will conduct primarily two kinds of observations,
interferometric  imaging and beamforming. All interferometric imaging
observations will, by definition, be spectroscopic. For a given
subarray operating in ``interferometric mode'', each pair of antennas
will be cross-correlated to provide full-polarization visibilities
across the requested bandwidth and number of channels.

In the ``beamforming mode'' each subarray can form several tied-array
beams and process data for each beam independently:

\begin{itemize}

\item SKA1-MID will be able to form up to 1500 ``Pulsar Search'' beams,
spread over up to 16 subarrays, each covering 300 MHz, based on the
selected antennas within 10 km of the subarray center. Similar operations
are anticipated for SKA1-LOW for up to 500 beams.

\item Both MID and LOW telescopes will be able to form up to 16 ``Pulsar
Timing'' beams. The setup will be similar to the ``Pulsar Search'' one, with
the exception that each beam will cover full input bandwidth for the observing
band.

\end{itemize}

The output of the CSP will be forwarded to the ``Science Data
Processor'' (SDP)\footnote{For more details see
\url{https://www.skatelescope.org/sdp}.}  for further reduction and
post-processing in order to derive scientifically useful results.  The
objective of the SDP subsystem is to build the necessary data analysis
software and pipelines, and the necessary hardware platform on which
these ``realtime'' or pseudo-realtime pipelines will run. The details
of the SDP data products are still being worked out but it is
anticipated that at least calibrated visibilities and
continuum and/or spectral-line image cubes will be made available to SKA
scientists.  The SDP operations will naturally take place close to the
telescope sites  and the results will be stored somewhere not too far
away. There is a  plan/desire to have SKA data centers set up across
the world, which will host copies (or subsets) of the SKA data
archives, where scientists can access the processed SKA data
products. These centers are expected to be places where the vast
majority of the scientists will interact with and analyze the SKA
data. Formally, they lie outside the scope of the SKA project and are
being financed independently by the SKA member countries.

SKA is expected to have a set of Key Science Projects (KSPs)
(typically with observing requirements of order 1000 hours or more)
and also ``Principal Investigator'' (PI)-driven projects. The KSPs are
still being formulated and the division of observing time between KSPs
and PI-driven projects is unclear. SKA will also have the requirement
to distribute observing time roughly in proportion to the
contributions by the member countries, although final decisions have not
been reached yet.

\section{Solar observations with the SKA1}

Scientists interested in using the SKA for their research have formed
``Science Working Groups'' (SWGs) which are advisory groups that
provide input to the SKA Organization (SKAO) ``...on the design,
commissioning, and future operations of the SKA that are likely to
affect the Observatory's scientific capability, productivity, and user
relations''\footnote{Excerpt taken from the Terms of Reference for
SKA's SWGs (see \url{https://tinyurl.com/ycmtjdrt}).}

One of them is the ``Solar, Heliospheric and Ionospheric'' (SHI) SWG\footnote{https://www.skatelescope.org/shi/}.
It  has more than 60 members from four continents and 20 countries and
it is currently chaired by E.P. Kontar (Glasgow) and  D. Oberoi (Pune).
The scientific interests  of the SHI SWG include the quiet Sun,
non-flaring active regions (ARs),  solar flares, CMEs, the  solar
wind, the Sun-Earth system, and the ionosphere.

The SHI group investigates the feasibility, hardware-wise, of solar
observations with both SKA1-LOW and -MID.  The SKA will be
able to observe the Sun both in interferometric imaging and beamforming
modes (see Section 2.2).

Low-frequency solar radio burst observations are in many ways similar
to observations of bright astrophysical radio sources and many general
purpose techniques can be ported to solar observations.  As for the
SKA1-MID, it has been established that: (1) the dishes can be pointed
to the Sun without raising the temperature of the receiver box by an
unacceptable amount, and (2) the low-noise amplifiers  themselves are
not expected to be saturated by the slowly-varying solar radio
emission or even solar radio bursts because they have been designed to
have sufficient  head-room to be able to deal with the occasional
presence of strong radio-frequency interference. On the other hand,
for the digital sampling of  the data  there will be a need to adjust
the gains/attenuations at appropriate  stages in the signal chain to
ensure that the sampling levels chosen are  appropriate for the range
of the voltages spanned by the solar signal.

Another important issue is that simultaneous observations with the LOW
and  MID arrays (especially of transient phenomena) will be very
difficult due to the large separation of the two arrays.  Simultaneous
observations at the three SKA1-MID Bands (see Section 2) will be
possible, in principle. This will, however, require configuring the
array as three independent sub-arrays operating at each of the three
bands.

Beamforming observations of the Sun will be possible by using the
pulsar setup briefly described in Section 2.2. The observing requirements
of the pulsar setup in terms of time and frequency resolution will be
more extreme than those needed for solar observing. The large number of
beams that will be provided simultaneously will be sufficient to tile the
SKA1-MID beam and the whole Sun in the case of SKA1-LOW.

As mentioned in Section 2.2, the development of the SDP is still
in its early phases. Details of the data products it will eventually
deliver are under discussion and the computational requirements to
meet them are being estimated. No software tailored to the unique
snapshot spectroscopic imaging requirements of solar observations has
yet been developed either by the SKA project or by the SHI SWG. However,
the solar and heliospheric science team of the MWA, a SKA precursor,
has recently developed an automated interferometric solar imaging
pipeline, a first step towards building experience and understanding
the issues associated with solar imaging from this class of
instruments (Mondal et al., in preparation).

\section{Solar radio emission mechanisms}

The electrons that produce solar radio emission can be either thermal
or nonthermal and the emission mechanisms either coherent or
incoherent
\citep[see][for more detailed reviews]{1985ARA&A..23..169D,Nindos08,Pick08}.

The most usual incoherent mechanisms are free-free emission and
gyroemission.  The former is generated when free electrons interact
with ambient ions via Coulomb forces and is therefore
ubiquitous. Radio emission  is produced when the relevant particle
populations are part of the same thermal distribution and provides
diagnostics of temperature, density, and (to some extent) magnetic
field.

Gyroemission is produced when free electrons are accelerated in a
magnetic  field because they experience the magnetic part of the
Lorentz force.  In the literature gyroemission is referred to as
gyroresonance emission when nonrelativistic electrons are involved and
gyrosynchrotron when mildly relativistic electrons are involved. In
the former case, the  emission comes from hot ($T_e \sim 10^6$ K)
thermal plasma interacting with  magnetic fields in excess of 100
G. It is very sensitive to magnetic field strength and orientation
\citep[e.g.][]{Zheleznyakov70} and generates microwave  emission at low
harmonics of the gyrofrequency above sunspots with strong  magnetic
field. Gyrosynchrotron is the basic microwave process in flares and is
produced by thermal or nonthermal energetic electrons (tens of keV to
several MeV) at harmonics ~10-100 of the gyrofrequency. In addition to
the magnetic field strength and orientation, the emission is also
sensitive to the properties of the radiating electrons
\citep[e.g.][]{Fleishman03b,Fleishman03a}.

The most important coherent emission mechanism is the plasma emission
mechanism \citep[e.g.][]{Melrose80}. It involves the formation of
non-equilibrium electron distributions, which excite plasma waves via
nonlinear processes. The plasma waves can be coverted in part to
electromagnetic waves at the plasma frequency ($\nu_{pe}=9\sqrt{n_e}$
kHz, where $n_e$ is the number density in cm$^{-3}$)  and/or its
second harmonic, $2\nu_{pe}$, via scattering off thermal ions or
coupling to ion-acoustic waves. Radio emissions via the plasma
mechanism are called type III bursts when they are associated with
upward-propagating beams of energetic electrons and type II bursts
when the energetic electrons are accelerated in MHD shocks.

Transient plasma emission is often the brightest solar emission and is
typically observed  at decimeter and longer  wavelengths. The
relevant flux densities may exceed 10$^5$ sfu \citep[e.g.][]{Pick05b} while
the associated brightness  temperatures may lie in the range of
10$^9$-10$^{12}$ K \citep[][]{Sainthilaire13}. On the other hand the
large-scale quiet free-free flux density may  range from less than 1 sfu to
more than 100 sfu ($T_b$ from $\leq 10^6$ to  $\sim$10$^4$ K,
respectively) as we move from low to high frequencies in the SKA
frequency range \citep[e.g.][]{Benz09}. Furthermore, gyroresonance-associated
flux densities may reach 10 sfu ($T_b \sim 10^6$ K) while the gyrosynchtron
mechanism may yield flux densities in excess of 1000 sfu ($T_b > 10^7$ K) at
short microwaves \citep[e.g.][]{Nita02}, and as weak as 0.01 sfu ($T_b \sim
100$ K) in the meter-wave band \citep[e.g.][]{Bastian01,Tun13}.

The above discussion indicates that high dynamic range imaging
is needed to map both the features associated with plasma emission
and those associated with other mechanisms. Probably the most
extreme requirements are posed by the need to map both the plasma
and free-free emissions in CMEs (see Section 9.1) where a dynamic
range of at least 10$^4$ is needed. The dynamic range of SKA1 images
will certainly exceed that value because one of its precursors
(i.e. the MWA) is already  able to exceed it (Mondal et
al. 2018, in preparation). SKA1 images with dynamic range of about
10$^5$ appear to be feasible although one cannot  guarantee values
of about $10^6$ or higher.

The weakest solar radio emissions are associated with tiny transient
activity originated from either free-free or gyrosynchrotron mechanism
(see Section 7). In the literature the weakest among such events have
been presented by \citet{Krucker97} (flux densities down to 0.002 sfu in
events detected at 15 GHz). It is not known whether there exists a
lower limit for the flux density of such weak events but SKA1 unprecedented
sensitivities (see Table 2) will help us detect them down to
levels not achievable before.

\section{Plasma diagnostics of the nonflaring Sun}

In the weak magnetic field regions of the non-flaring Sun, the radio emission
comes from the free-free mechanism. The radiation is formed in local
thermodynamic equilibrium (LTE) and the source function is Planckian. For
radio frequencies the Rayleigh-Jeans approximation is valid and the observed
intensity is proportional to the kinetic temperature of the emitting plasma
for optically thick sources (in stark contrast to the situation in optical
and UV wavelengths).

\begin{figure}
\centering
\includegraphics[scale=0.40]{fig3.eps}
\caption{Images of the Sun on 2004 June 27. From left to right and from top
to bottom: NRH images at 432, 410, 327, 236, 164, and 150 MHz, NoRH image
at 17 GHz and soft X-rays image from SXI on board GOES12.
After \citet{Mercier09}. Reproduced by permission of the
AAS.}
\label{fig3}
\end{figure}

The highest frequencies that will be accessible with SKA1 ($3 \lesssim
\nu  < 15$ GHz) are optically thin (an example appears in the 17~GHz
image  of Figure~\ref{fig3}) and we see down below the transition
region (TR): the higher the frequency the deeper we see. At such high
frequencies the only regions above the chromosphere that may  become
optically thick are associated with sunspots of strong magnetic field
where gyroresonance  absorption could become significant. At
frequencies between 1 and  3 GHz the non-flaring corona is
optically thin except  over active regions where hot, dense loops
may render it  optically thick to free-free
\citep[e.g.][]{White99}. At decimeter and longer wavelengths the
emission is optically thick and TR/coronal brightness temperatures are
expected.  Examples of images, produced using rotational synthesis
imaging, at such  low frequencies (obtained with
the NRH at 150-432  MHz) appear in Figure~\ref{fig3}.  The figure
shows that the similarity of the soft X-ray image with the NRH images
decreases as frequency decreases.  This cannot be attributed to a
spatial resolution effect only \citep[][]{Kontar17}.  Apart from
refraction effects that are at work in radio
\citep[e.g.][]{Alissandrakis94,Shibasaki11}, the optical depth of the
radio emission is appreciable.  Therefore these radio  images probe
higher layers of the corona, and lower-lying X-ray-emitting
structures are obscured by overlying dense material. The same
arguments  explain the little resemblance between the NRH images and
the 17 GHz image.

Using the SKA1 frequency bands we will be able to sample, with
unprecedented angular and spectral resolution, the thermal state of
optically thick structures (e.g. the quiet Sun, coronal holes, active
regions, and filaments)  at heights above the chromosphere.  We also
note that there is a lack of imaging of the Sun at frequencies from
0.45 GHz to 1 GHz.  With SKA1-MID Bands 1 and 2 (frequencies from 0.35
to 1.76 GHz) we will be able to image that frequency range
(MUSER, however, may obtain images at that frequency range
before  SKA1).

\section{Coronal magnetography}

Due to inherent difficulties in measuring the Zeeman effect
in the corona \citep{2004ApJ...613L.177L},
radio methods are of primary importance in obtaining quantitative
information about its magnetic field.

\begin{figure}
\centering
\includegraphics[scale=0.50]{fig4.eps}
\caption{Iso-Gauss surfaces corresponding to the third harmonic of the
gyrofrequency at 5, 8 and 11 GHz, together with lines of force of the
extrapolated magnetic field for an active region. From \citet{Lee07}.
Reproduced with permission {\textcopyright}Springer
Nature.}
\label{fig4}
\end{figure}

\subsection{Coronal magnetic field from gyroresonance emission}

Gyroresonance  emission is a valuable tool for magnetic field
measurements above sunspots. There are several publications on the
subject particularly after the first modeling of high-resolution
observations by \citet{Alissandrakis80}. More recent publications have
been reviewed by \citet{White97} and \citet{Lee07}.

The gyroresonance emission observed at a given frequency originates
from a  narrow iso-gauss layer where the frequency matches a low
harmonic of the  gyrofrequency (see Figure~\ref{fig4}).
The gyroresonance opacity \citep[][]{Zheleznyakov62}
is much higher in the $x$-mode than in the $o$-mode,
and at the second harmonic than at the third.
Above sunspots, the third harmonic is opaque in the $x$-mode but not in the
$o$-mode, and the second harmonic is opaque in both modes. Emission
from the fundamental  is not observed, both  because it is obscured by
the overlying second harmonic  layer and because of propagation
effects, while emission at the fourth harmonic can appear at long
centimeter wavelengths.

For low photospheric magnetic fields or/and high frequencies both the
third  and second harmonic layers are below the TR and  no strong
gyroresonance  emission is expected. The third harmonic layer enters
into the TR for appropriately higher values of the field or lower
frequencies and yields strong, almost 100\% polarized, emission
\citep[e.g.][]{Shibasaki94,Nindos00}. The second harmonic
layer enters the TR for even higher field intensities or lower
frequencies and then the polarization drops.  Therefore the brightness
temperature spectra of both total intensity ($I$) and circular
polarization ($V$) show a rapid rise at the wavelength where the third
harmonic enters into the TR; the magnetic field at the base of the TR
can be estimated from the extrapolation of the $V$ to zero and the
equation $\nu = s \nu_{ce}$ with harmonic number $s = 3$. The potential
of this technique has been demonstrated in several publications that
use OVSA \citep[e.g.][]{Gary87,Gary94} and RATAN-600 spectral data
\citep[e.g.][]{Akhmedov86,Korzhavin10}. Note also that
such measurements are now routinely available from RATAN-600 data and
can be found at \url{http://www.sao.ru/hq/sun}.

SKA1-MID Band 5 (4-15 GHz) observations will provide a brightness
temperature  spectrum along each line of sight through the
gyroresonance source, thereby  enabling the assembly of a map of the
magnetic field at the base of the TR. Given the fact that when a
harmonic layer is opaque the observed brightness temperature is equal
to the local electron temperature, the 3D structure of the coronal
magnetic field could also be constrained \citep[e.g.][]{Tun11} because
the SKA1-MID's spectroscopic imaging observations could yield the
variation of the magnetic field strength as a function of temperature
along each line of sight through the gyroresonance source, provided
that one identifies the harmonic(s) that contribute to the
gyroresonance emission at each frequency.  The dense spectral coverage
that will be provided by SKA1 will yield complete sampling of a large
part of the TR/coronal volume over sunspots, and therefore continuous
magnetic field strength coverage.

\subsection{Coronal magnetic field from propagation effects}

When radio emission passes through a region where the longitudinal
component of the magnetic field changes sign, its sense of circular
polarization reverses when the coupling (which depends on the magnetic
field strength and the gradient of the angle between the line of sight and
the field along the ray path, as well as the electron density and the
frequency of observation)  between the $x$- and $o$-modes is weak and
does not change when the coupling  is strong \citep[e.g.][]{Bandiera82}.
For intermediate ``critical'' coupling the polarization becomes
linear. The  line that delineates the reversal in the sense of
circular polarization ($V=0$) is known as ``depolarization strip''.

In depolarization strips one can estimate the magnetic field under
some assumption about the electron density \citep[e.g.][]{Kundu84}.
The extension of this method for cases of partial depolarization
allows for the computation of a coronal magnetogram over the
quasi-transverse layer (i.e. the region where the magnetic
field is almost perpendicular to the direction of propagation of the
radiation), provided that the intrinsic polarization of  the waves
is known, for example by using polarization data before the mode
coupling occurs \citep[see][for details]{Ryabov99,Ryabov05}.

Polarization inversion provides diagnostics about the coronal magnetic
field  at heights of about 0.05-0.4$R_{\odot}$, and is independent of
the emission mechamism. Therefore all SKA1-MID Bands could be
used to  exploit the potential of the method: their dense spectral
coverage will allow to locate the coronal regions where the field is
perpendicular to the line of sight and to derive information about the
magnetic field well above the formation height of the microwave
emission.

\subsection{Magnetic field from free-free emission}

The weak polarization of the free-free emission in the sense  of the
$x$-mode can be used to determine
the longitudinal component, $B_l$, of the magnetic field:
for an optically thin slab above a uniform background
it is easy to show that $B_l$ is proportional to the degree
of circular polarization, $\rho$, and the frequency.
Things are more complicated in the general case, where
physical conditions vary with height.
When spectral observations are available,
one can use the approximate expression \citep{Bogod80,Grebinskij00}
to determine $B_l$:
\begin{equation}
B_l \approx 107 \frac{\rho (\%)}{n \lambda},
\end{equation}
where $B_l$ is in G, $\lambda$ is the wavelength in cm,
and $n = - \ln T_b / \ln \nu$ the spectral index.
This expression allows for temperature variations
in the  radiation-formation region and
its validity is not limited to the  optically thin case,
although it implicitly assumes constant magnetic field.
The combination of SKA1-MID's unprecedented sensitivity and high
frequency resolution will allow, for the first time, to constrain the
longitudinal  component of the coronal magnetic field to a few Gauss.

An extension of the above method could be used to provide estimates of
the magnetic field strength of undisturbed streamers at higher
altitudes (heliocentric distances of 1.5$R_{\odot}$ to
2.5$R_{\odot}$) by measuring the degree of circular polarization of
the associated free-free emission using SKA1-LOW observations
\citep[see][for details]{Sastry09,RameshSastry10}.

\section{Coronal heating}

Coronal heating remains one of the major unsolved problem in solar physics.
The proposed mechanisms to heat the corona
\citep[e.g. see][for reviews]{Klimchuk06,Demoortel15}
are divided into two broad classes:
waves and small-scale reconnection events, also known as
nanoflares. Acoustic wave heating has been a favorite for the non-magnetic
chromosphere, but it appears that the appropriate waves
do not  carry enough energy \citep[][]{Fossum05}.
Other types of waves, such as Alfven waves in the
presence of turbulence \citep[][]{Vanballegooijen11} could be an alternative.

\begin{figure}[t]
\centering
\includegraphics[scale=0.70]{fig5.eps}
\caption{MWA dynamic spectrum with numerous nonthermal, weak (0.6-307 sfu)
narrow-band (4-5 MHz), short-lived (1-2 s) bursts. This figure has been
constructed with data presented in \citet{Suresh17}.}
\label{fig5}
\end{figure}

There have been several efforts to search radio data for small-scale
transient events that could potentially contribute to coronal
heating. These efforts are partially inspired by the sensitivity of the
radio domain to small  populations of nonthermal electrons that could
arise in the course of  reconnection. At microwaves such studies
\citep[e.g.][]{White95,Krucker97,Gary97,Nindos99,Benz99}
have shown that tiny transient activity may occur both within
and away from ARs and that in several cases the events show
flare-like properties being either thermal or nonthermal.
At lower frequencies short duration small isolated bursts have also been reported
\citep[e.g.][-see Figure \ref{fig5}]{1986ApJ...308..436K,Ramesh10,Sainthilaire13,Suresh17}.

Several authors \citep[e.g.][]{1984ApJ...283..421L,Gary99,2000ApJ...535.1047A,2002ApJ...572.1048A}
have computed histograms of the energy distribution
in impulsive events using X-ray and EUV data.
However, the low energy part of flaring events
is poorly known, hence nanoflare heating model \citep{1988ApJ...330..474P}
evades observational confirmation.

SKA1 could provide significant insights into the coronal
heating problem because: (1) it will provide detailed time series of
the temperature, density, and magnetic field in various coronal
structures (see Sections 5 and 6) from which the rate of energy
storage into the corona could be estimated as a function of position
and time and then checked against wave heating model predictions,
(2) due to its unprecedented sensitivity, angular, temporal and spectral
resolution, as well as wide field of view, SKA1 will be able to detect
weak, small, short-lived, narrow-band transient events down to levels
not achievable earlier, over large parts of the solar disk.
The computation of the occurrence rate and energy budget of these events
will help us derive more accurate constraints than ever before
and evaluate their role in coronal heating.

\section{The physics of flares}

Through magnetic reconnection, flares release large amounts of magnetic
energy  stored in the corona which accelerates particles
and heats extended layers of  the solar atmosphere.
Accelerated particles emit at radio wavelengths, X-rays, and in some cases gamma-rays \citep[see][for a review]{2011SSRv..159..107H}.
The hard X-rays typically arise from the interaction of electrons
with energies from a few tens of keV to a few hundreds of keV
with chromospheric plasma via the nonthermal free-free mechanism.
On the other hand, radio emission may arise either from suprathermal electrons
that produce coherent radio emission due to plasma instabilities or from
mildly relativistic electrons that emit nonthermal gyrosynchrotron
radiation. X-ray and radio observations complement each other
\citep[e.g.][]{White11} and both are essential to study particle
acceleration and transport. Radio observations provide the advantage
that not only are they sensitive to anisotropies in the electron
distribution function, but also uniquely sensitive to the magnetic
field.

\subsection{Electron acceleration}

Flare energy release and particle acceleration appear to be
spatially fragmented processes, where the acceleration region
may not coincide with the region of magnetic energy
release \citep[e.g. see the reviews by][]{Bastian97,Zharkova-ssr11}.
Furthermore, the energy partition \citep{2012ApJ...759...71E,2017ApJ...836...17A}
and the efficiency of  the particle acceleration may vary from event to event,
from purely thermal \citep[e.g.][]{Gary89} to acceleration-dominated
\citep[e.g.][]{Krucker10,Fleishman11}.

The high sensitivity of radio emission to nonthermal electrons makes it
possible to probe rather tenuous electron acceleration sites that could
not be detected by hard X-rays which require higher densities
as observed in some events \citep{2008ApJ...673..576X,2011ApJ...730L..22K}.
Radio diagnostics of the electron acceleration region include
(1) decimetric type III bursts,
(2) decimetric narrow-band spikes,
and (3) microwave narrow-band gyrosynchrotron bursts.

Type III bursts are plasma emissions resulted from the propagation of
beams of energetic electrons along open field lines
\citep[see][for reviews]{1985srph.book..289S,Reid14a}.
Of particular interest are the decimetric type III bursts  that usually (but not always)
occur in the 400 MHz to 1 GHz frequency range which corresponds to densities of
$2-12 \times 10^9$ cm$^{-3}$; i.e. to the  heights where flare energy
release occurs \citep[e.g.][]{Benz04}. \citet{Reid11,Reid14b} combined
hard X-ray spectroscopic data and radio dynamic spectra of type III bursts
to find that the acceleration region is located well above soft X-ray
flaring loop tops at heights between 25 to 200 Mm. This result is
consistent with earlier findings by \citet{Aschwanden97}.

The potential of exploiting decimetric and metric type III bursts for
the  diagnosis of the electron acceleration site is hampered by the
fact that  relevant multi-frequency imaging observations are rare and
only at a few discrete frequencies
\citep[e.g.][]{Aurass97,Paesold01,Alissandrakis15}.
Probably the only imaging spectroscopic observation of a type III
burst has been reported by \citet{Chen13} who found that the radio data
indicated that the energy release showed fragmentation in space and time,
suggesting a bursty reconnection scenario.

Among the coherent transient emissions at decimetric wavelengths,
spikes are expected to show the closest relation to the electron
acceleration region because (1) they show the highest correlation with
hard X-rays \citep[e.g.][]{Benz86,Aschwanden92}
and (2) they occur at the rise phase of the flare \citep[][]{Slottje78}.
However, studies of the locations of decimetric  spike bursts and hard X-ray sources
suggest the presence of a secondary acceleration region high up in
the corona, away from the flaring site \citep[][]{Benz02,Khan06,Battaglia09}.

\citet{Fleishman11,Fleishman13,Fleishman16} have shown
that narrow-band microwave  gyrosynchrotron radiation
which is emitted directly from the accelaration  region can be detected
when the trapped electron population is negligible.
This emission distinguishes itself from the usual broadband gyrosynchrotron
emission due to the steep energy spectrum of electrons accelerated
in a rather uniform source.

\subsection{Electron transport}

Electron transport during flares is usually discussed in relation to
the dynamics of both the radio and associated hard X-ray emission. The
most widely used model is the ``direct precipitation/trap plus
precipitation'' (DP/TPP) model \citep[e.g. see][as reviews]{Bastian98,Aschw-ssr02}.
Briefly, the magnetic field guides accelerated
electrons with small pitch  angles to the chromosphere, where the
dense plasma stops them \citep[e.g.][for a review]{2011SSRv..159..107H}.
The largest part of their energy heats the ambient chromosphere
while a smaller part is emitted in HXRs via the nonthermal
``thick-target'' free-free mechanism.
Electrons with sufficiently large pitch angles are trapped in the flaring loop
and produce gyrosynchrotron emission.
Eventually, they are scattered into the loss cone through wave-particle
interactions or Coulomb collisions and precipitate into the chromosphere,
producing additional hard X-ray emission.
Microwave gyrosynchrotron emission does not come
exclusively from trapped  electrons;
in several studies microwave emission has been reported
from the precipitating electrons \citep[e.g.][]{Kundub01,Lee02}
or from electrons that are efficiently scattered \citep{2018A&A...610A...6M}.

The observed signatures of gyrosynchrotron radiation are sensitive
to anisotropies in the electron distribution function \citep[e.g.][]{Lee00}.
However, it is not always straightforward to deduce whether
the anisotropies stem from the injection/acceleration of the electrons
or from transport effects \citep[e.g.][]{Melnikov02} and it appears
that acceleration and transport are interwined in some cases
\citep[e.g.][]{Bastian07}.

\subsection{Magnetic field diagnostics in flaring loops}

The spectral and spatial structure of microwave gyrosynchrotron
emission from flaring loops has a strong dependence on the magnetic
field and the properties of energetic electrons. The spectral peak
divides the spectrum into an optically thick low frequency part and an
optically thin high frequency part. In a flaring loop the magnetic
field is strongest near the footpoints and decreases toward the loop
top.  Therefore, at a given frequency the higher the energy of the
electrons, the  closer to the flaring loop top will they
emit. Consequently, for a homogeneous  isotropic distribution of
energetic electrons, at high frequencies we expect  to obtain
optically thin emission primarily from the footpoints of the flaring
loop \citep[e.g.][]{Alissandrakis93} while more extended optically
thick  sources should appear with the decrease of the  frequency of
observation \citep[e.g.][]{Wang94}.
Anisotropies or/and inhomogeneities in the  properties of the electrons
may modify the above picture, for example by  the development of optically
thin loop top sources due to high concentration of energetic electrons there
\citep[][]{Melnikov02} \citep[see also][]{Kundu01,White02,Tzatzakis08}.
An example of the diversity of gyrosynchrotron source morphologies is
presented in Figure~\ref{Fig7}.

\begin{figure}
\centering
\includegraphics[scale=0.50]{fig6.eps}
\caption{A large flaring loop observed at 17 and 34 GHz with the NoRH.
Contours are at 10\% intervals of 550 and $170 \times 10^6$ K at 17 and
34 GHz, respectively. From \citet{Tzatzakis08}. Reproduced with
permission {\textcopyright}Springer Nature.}
\label{Fig7}
\end{figure}

The above discussion indicates that the use of gyrosynchrotron
emission for diagnostics of the magnetic field is not as
straightforward as in the case of gyroresonance.
For reliable diagnostics one would need to combine detailed modeling
of the gyrosynchrotron emission
\citep[e.g.][]{Klein84,Alissandrakis84,Bastian98,Fleishman10,Simoes10,Kuznetsov11,2015ApJ...799..236N}
with spectroscopic imaging observations.
Thus any information on the magnetic field comes as a result of modeling.
In spite of the difficulties, modeling of individual events observed either by the VLA
and OVSA \citep{Nindos-white00}  or by the NoRH and the Nobeyama
Polarimeter \citep[e.g.][]{Kundu04,Tzatzakis08,Kuznetsov15} have yielded
magnetic field strengths ranging between 1700 G at the footpoints
and 200 G at the loop top.

\subsection{SKA's contribution to flare research}

The discussion in Sections 8.1-8.3 indicates that despite the
significant recent progress, several fundamental questions about the
physics of flares  remain unanswered.
These questions include: (1) The location of  electron acceleration,
its magnetic configuration, and its relation to the  site of energy release.
(2) The mechanism(s) responsible for electron  acceleration
and the conditions under which they operate.
Several acceleration models  have been proposed
\citep[e.g. see][for reviews]{Zharkova-ssr11,Klein17} but all of  them
are in need of reliable
observational inputs. (3) The accurate  determination of the
distribution function of the energetic electrons and its evolution in
space and time. (4) The factors that determine the efficiency with
which magnetic energy is converted into energy of nonthermal
particles.  (5) The physical processes responsible for  the transport
of accelerated electrons and how one can disentangle
injection/acceleration from transport effects.

The unique capabilities of SKA1 have the potential to provide
significant advances in addressing the above questions. First of all,
SKA1 will provide the means to perform coronal magnetic field
measurements before,  during, and after flares (see  Section 6), thus
allowing the determination of the magnetic free energy that  becomes
available. The relevant results will be superior from the ones
provided by nonlinear force-free extrapolations of the photospheric
field because the latter provide non-unique solutions
\citep[e.g.][]{DeRosa09}, rely on field measurements  in layers where
the field is not force-free \citep[][]{Metcalf95}  and their cadence
is not sufficient to capture the impulsive  evolution of energy
release and particle acceleration. Spectroscopic imaging observations
will  allow to establish the location of  electron acceleration and to
provide important constrains on the relevant acceleration
mechanisms by revealing, in unprecedented detail, the properties of
the  bursts that are believed to be intimately  related to the
acceleration process, and most probably by discovering new relevant
diagnostics.  The combination of forward fitting techniques with
high-cadence spatially  resolved spectra of the gyrosynchrotron
emission will allow to constrain both the properties of the electron
distribution function and the magnetic field in the flaring volume
more accurately than ever before.

\section{Large-scale transient activity and space weather}

\subsection{Coronal mass ejections}

All CME constituents emit radio radiation
\citep[see][for a review]{Gopal11}.
Eruptive prominences that later will evolve into
the cores of white-light CMEs are observed at microwaves via the
thermal  optically thick free-free emission that they  emit
\citep[e.g.][]{Hanaoka94,Gopalswamy96,Gopalswamy03,Grechnev06,Gopalswamy13}.
These observations complement
the usual  H$\alpha$ observations and have the advantage that the
continuum free-free emission can be detected even when the material is
heated to high temperatures that make it undetectable in
H$\alpha$. Higher up, one anticipates production of optically thin
free-free emission from the whole CME that could be detected at lower
frequencies. However such observations are rather rare
\citep[e.g.][]{Sheridan78,Gopalswamy92,Kathiravan02,Ramesh03}
because the relevant emission is weak (due to the  high
temperatures and low densities that usually prevail in CMEs) and often
outshined by the stronger nonthermal emissions. When detected, the free-free
emission from CMEs provides an alternative way to estimate their masses
\citep[][]{Gopalswamy92}.

\begin{figure}
\centering
\includegraphics[scale=1.00]{fig7.eps}
\caption{(a) Image of a CME at 164 MHz computed from NRH data. The spectral
index estimated at the locations of the four white dots is also marked. (b)
Flux spectra estimated at the points marked in (a) accompanied by model
gyrosynchrotron spectra. From \citet{Bastian01}. Reproduced
by permission of the AAS.}
\label{fig8}
\end{figure}

At radio dynamic spectra, CME-related emissions include type II bursts
(see Section 9.2)  as well as stationary and moving type IV bursts. The
stationary type IV bursts emanate from electrons trapped in
post-eruption  arcades behind CMEs while the moving ones correspond to
CME-related  outward-moving material. Stationary type IV bursts should
arise from  plasma emission mechanism, while plasma emission
\citep[e.g][]{Duncan81,Stewart82,Gopal89,Klein02,Ramesh13,Hariharan16},
and more rarely gyrosynchrotron emission from nonthermal electrons
\citep[][]{Gopal87,Bastian01,Maia07,Tun13,Bain14,Carley17} have beeen
invoked for the interpretation of the properties of moving type IV bursts.
The detection of gyrosynchrotron emission from some CMEs
(see Figure~\ref{fig8} for an example),
is important because, if combined with modeling (see Section 8.3),
it could  provide estimates about the CME magnetic field; in the publications
cited above, CME magnetic fields from 15 to 0.1 G have been reported at
heights from $1.3R_{\odot}$ to $2.8R_{\odot}$.

Radio imaging observations of the early development of CMEs, albeit at
few frequencies only, have  revealed a large diversity of magnetic
configurations that produce energetic electrons
\citep[e.g.][]{Klein01,Pohjolainen01,Maia03,Pick05a,Pick06,Demoulin12,Carley16}.
Such observations are a necessary ingredient for any validation of CME
initiation models because nonthermal radio emissions could highlight
possible locations of magnetic reconnection.

The potential of radio observations to CME research has not been fully
exploited because of their lack of spectroscopic imaging capabilities
and their inadequate sensitivity. SKA1 capabilities promise to change
that situation. First of all, SKA1's high angular, spectral, and
temporal resolution will provide, for the first time, a comprehensive
picture of CMEs over extended frequency ranges. Since plasma emission
probes the plasma frequency  level or/and its second harmonic the
resulted radio morphologies may be different from the white-light CME
morphologies, therefore for non-incremental  progress, one should be
able to image both the thermal free-free emission and  the much
stronger plasma emission simultaneously. For this task
a dynamic range of at least 10$^4$ is required (see the discussion
in Section 4) which should be well within SKA1's capabilities.
We also note that according to \citet{Bastiangary97}
the optimum frequency range for the detection of free-free
emission from CMEs is between $0.2-2$ GHz (i.e. within SKA1's frequency
range).

SKA1-LOW will be ideal to probe the early development of CMEs
(including earth-directed ones whose detection by coronagraphs at L1
might be difficult at times), study the flare-CME relationship, and
determine the sites of CME-related electron acceleration. SKA1-LOW's
wide  field of view will allow to study the effects of CMEs on the
surrounding plasma and their evolution  into interplanetary
disturbances. Finally, the spectroscopic imaging capabilities of the
instrument combined with its high sensitivity also promise more
frequent detections of gyrosynchrotron emission from CMEs, and
consequently the development of a statistically significant sample of
CME magnetic field estimates.

SKA1 will also play a key role in studying CMEs in the interplanetary
medium. Along with the more traditional interplanetary scintillation
studies, heliospheric science with the SKA is also  expected to
include studies of the Faraday rotation of linearly polarized
background radiation due to the magnetized solar wind and CME
plasma. In this article we restrict ourselves only to a discussion of
the solar physics questions which can be addressed with the SKA1. While
important and interesting, the heliospheric physics to be pursued by the SKA1
lies outside the scope of this article. Interested readers are referred to the
review by \citet{Nakariakov15} for a short discussion of these topics.

\subsection{Coronal shocks}

Type II bursts are plasma emissions resulting from the propagation of
MHD shocks in the corona; the emission appears as narrow-band lanes at
the plasma frequency or/and its second harmonic
\citep[see the reviews by][]{Nelson85,Vrsnak08,Pick08,Nindos08}.
Although interplanetary type II bursts are generated exclusively by
CME-driven shocks \citep{Gopalswamy06}, the combination of radio imaging
observations with coronagraphic, EUV, and soft X-ray data show that
coronal shocks could appear close to either the leading edge
\citep[e.g.][]{Maia00,Ramesh12} or the flanks of CMEs
\citep[e.g.][]{Cho07,Zucca14}, ahead of erupting flux
ropes \citep[][see Figure 8]{Bain12,Zimovets15},
above
expanding loops \citep[][]{Klein99,Dauphin06}, in
conjunction with jets that erupt in the course of CMEs \citep[][]{Zucca-etal14},
and ahead of EUV bubbles \citep[][]{Kouloumvakos14}.
CME deflections \citep{2016ApJ...823....5P} and streamer-CME interactions
\citep[][]{Kong12,Eselevich15} in the low corona could also play a
role in the generation of coronal shocks. Some coronal shocks are
flare-related \citep{Magdalenic08,Magdalenic10,Magdalenic12,Nindos11,Kumar16}
because either there was no CME or the timing of the CME did not match the
timing of the type II burst.

\begin{figure}[ht!]
\centering
\includegraphics[width=\textwidth]{fig8.eps}
\caption{Left: a complex type II burst observed by the ARTEMIS IV radio
spectrograph. Yellow diamonds mark precursor activity while the blue,
red, and green symbols mark the central frequencies of the three emission
lanes of the harmonic emission. Right: Contour plots of precursor (a) and
type II (b-d) second harmonic emission of the event in the ARTEMIS dynamic
spectrum. The background consists of AIA 131 \AA\ difference images.
After \citet{Zimovets15}. Reproduced with permission
{\textcopyright}Elsevier.}
\label{fig9}
\end{figure}

The above discussion indicates that coronal shocks could be produced
by a variety of drivers: CMEs, small-scale ejecta associated with
flares or flare pressure pulses. Some authors (e.g. Gopalswamy et al.
2005, 2009) have concluded that all metric type II bursts are
generated by CME-driven shocks and the popularity of this
interpretation is reinforced by the high association between metric
type II bursts and EUV waves, the latter being driven by the lateral expansion
of CMEs \citep[e.g.][]{Patsourakos12}. However, it is fair
to say that for a few events a flare origin cannot be excluded.

Progress in the study of coronal shocks has been limited by the
inadequate angular and spectral resolution as well as sensitivity of
radio imaging  instruments and by the fact that the coronal shock
emission that they  detect may come from heights occulted in
coronagraphs. SKA1-LOW's specifications promise significant advances
in our understanding of coronal shocks. With its superior
angular-spectral resolution and dynamic range, the instrument will be
able to image both  the CME and shock radio emission  simultaneously
which (combined with observations in the EUV and soft X-rays) will
help us identify unambiguously the role of each eruption constituent
to the development of  the shock from its earliest stages. SKA1-LOW's
wide field of view will also help us monitor the shock propagation and
evolution in the  corona, well above the heights obscured by the
occulting disk of coronagraphs.  Furthermore, the fine structure of
type II bursts \citep[e.g.][]{Mann05,Carley13,Mann18} will be recorded with
unprecedented detail which is an essential step to constrain shock
inhomogeneities and turbulence as well as the role of shocks in particle
acceleration.

\subsection{Origin of solar energetic particles}

Solar energetic particle (SEP) events are important for both the study
of particle acceleration and space weather
\citep[e.g.][]{Reames99,Gopal08,Vainio09,Valtonen11}. Since the
work by \citet{Reames99} SEP events are usually classified into two
groups: impulsive or  gradual depending on the strength and duration
of the parent soft X-ray flare, their association with type III or
type II/IV bursts, charge states and abundances of the energetic
particles, and the absence or presence of a CME. Impulsive events is
thought to originate from particle acceleration induced by
flare-related  magnetic reconnection while the accelearation of
gradual-event particles is thought to originate from CME-driven
interplanetary or/and coronal shocks.

The above dichotomy has been challenged by several particle and
radio/hard X-ray studies
\citep[e.g.][]{Klein-chupp99,Klein14,Laitinen00,Klein-trot01,Cane02,Klein05,Kouloumvakos15}
which indicate
that it is difficult to establish a clear distinction between
CME-associated and flare-associated SEP events. After all,
reconnection, for example, could occur not only during the impulsive
phase of flares but also in current sheets that are formed behind CMEs
while acceleration by shocks generated by the interaction of
reconnection outflows with loops in a cusp-shaped configuration
might also be possible \citep[e.g.][]{Aurass02,Aurass04,Mann09,Warmuth09,Chen13}.

Sections 8 and 9.1-9.2 indicate that SKA will probe in an unprecedented way
the  diverse agents of particle acceleration in the low and middle
corona and  therefore we expect that its observations will provide key
inputs that will help shed light on the controversies related to the
origin of SEPs.

\section{Synergistic activities}

SKA's construction overlaps with the operation and/or development of
important  new-generation ground-based and space-borne solar
instruments.

Ground-based facilities include Big Bear Solar Observatory's Goode Solar Telescope
\citep[in operation since 2009;][]{Goode12},
the Daniel K. Inouye Solar Telescope
\citep[][under construction with a planned completion date of 2019]{Tritschler15}
and the European Solar  Telescope
\citep[][under construction with a planned completion date of 2020]{Matthews16}.
These instruments observe (or could) observe the photosphere
and chromosphere in optical or/and near-infrared wavelengths
with unprecedented sensitivity (owing to their large apertures),
angular resolution ($\sim 0.1\arcsec$ using adaptive optics),
and polarization accuracy ($\sim 10^{-4}$ of intensity).
Their science objectives include the study of (1) solar magnetic fields
(their life cycle and their role in the initiation of transient activity),
and (2) the mechanisms of solar  variability.
The SKA will not be able to observe the layers probed by the above
instruments, but coordinated observations will be of major importance
providing a comprehensive picture of all layers of the solar atmosphere,
from the photosphere to the outer corona.

The most important forthcoming solar space missions
are the Parker Solar Probe \citep[PSP,][]{Fox16}
and the Solar Orbiter \citep[SO,][]{Muller13},
which are scheduled for launch in 2018 and 2020, respectively.
Both missions are designed to approach the Sun closer
than ever before (10 and 60$R_{\odot}$, correspondingly)
and carry several instruments for in situ measurements.
As for remote sensing instruments they will both be equipped
with heliospheric imagers while SO will also be equipped
with a vector magnetograph, instruments for EUV imaging and spectroscopy,
a telescope/spectrometer for thermal and nonthermal X-ray emission,
and a coronagraph. SKA1 and SO/PSP data will complement each other.
For example, due to their close approach to the Sun both SO and SPP could
measure SEP properties with minimal influence of transport effects,
while SKA1 will provide information about energetic electron seed populations
and the role of flares and CME-driven shocks in SEP acceleration.
The combination of SKA observations with data from the in situ  radio wave
instruments (available from both SO and PSP) will allow
to track (albeit spatially unresolved) CME-related emissions recorded
by the SKA1 into the interplanetary medium.
Measurements of the magnetic field in the lower solar atmosphere
by SO will complement the SKA1's coronal magnetography capabilities,
while the combination of SKA1 data with SO hard X-ray observations
could provide new opportunities to study flare electron acceleration
low in the solar atmosphere. SO/PSP synergies with the SKA1 will also
have a strong heliospheric component because SKA1 observations
could provide constraints  on turbulence and waves in the solar wind
\citep[see][for details]{Nakariakov15}.
Finally, needless to say that coordinated observations between the SKA1
and currently existing space instruments (e.g. SDO, RHESSI, STEREO, Hinode,
and IRIS) could also be very useful.

SKA1-LOW solar observations will overlap in time with solar-dedicated
radio heliographs that will observe at higher frequencies (NoRH,
MUSER, and Siberian RH). The temporal overlap could be exploited to
partially compensate for the most probable inability to operate the
SKA1-MID and LOW arrays simultaneously. The successful exploitation
and interpretation of several SKA1 observations will benefit from recent developments in
theory \citep[e.g.][]{Zharkova-ssr11,Hannah13,Kontar15,Kontar-perez17}
and simulations of solar radio emissions
\citep[e.g.][]{2011PhPl...18e2903T,Li12,Gordovskyy14,Schmidt14,2014A&A...572A.111R,Schmidt16}.

\section{Summary}

The SKA is a unique radio instrument which promises to transform
practically all branches of astrophysics due to its unique
specifications  which, even after completion of the Phase 1 of its
deployment (i.e. SKA1),  could significantly outperform all other
radio telescopes. Solar physics benefits immensely from the
deployment of the SKA because of the feasibility of solar observations
with both SKA1-LOW and SKA1-MID.
SKA1's unprecedented angular, spectral, and temporal resolution, as
well as sensitivity will provide major new insights into many important
solar physics problems.

Observations of the non-flaring solar atmosphere
will provide time series of its thermal state which can be
checked against solar-atmosphere heating models.
The detection of numerous weak transient events could
facilitate the derivation of reliable estimates about their
contribution to coronal heating in the framework of the
nanoflare model.

Several radio emission mechanisms/processes are uniquely
sensitive to magnetic field, and one of the most important outcomes
of SKA1 observations will be the direct and indirect measurements
of the magnetic field at heights unaccessible by other instruments.
The measurements can be used both for the computations of magnetic
free energy budgets as well as for the diagnosis of the magnetic field
of active regions, flaring loops, and CMEs.

SKA1 observations have strong potential to
provide a comprehensive view of coherent and incoherent emissions
that are intimately related to electron acceleration,
of gyrosynchrotron emission from precipitating
and trapped electrons in flaring loops, as well as of CMEs, shocks,
and related phenomena.
These observations have the potential to provide major advances
to key solar physics questions about:
(1) the location and magnetic configuration of the electron acceleration site,
(2) the mechanism(s) responsible for particle acceleration,
(3) the flare-CME relationship,
(4) the timing  and evolution of CMEs from the early stages
of development all the way to the outer corona,
(5) the drivers of coronal shocks as well as the locations
and efficiency of electron acceleration by shocks,
and (6) the origin of SEPs.

Above all, as is always the case with new instruments that outperform
their predecessors in a significant way, is the high probability of
new discoveries that cannot be predicted now.  This exciting prospect
is further highlighted by the availability of synergistic activities
between the SKA and the new generation of ground-based and space-borne
solar instruments.

\section{Acknowledgements}

We acknowledge the activities of the members of the SHI SWG
toward the goal to exploit SKA's capabilities for solar physics
research. We thank the referees for their comments which led to
improvement of the paper. EPK was supported by  STFC consolidated
grant ST/P000533/1. DO was partially supported by a grant  from the
Department of Atomic Energy, Government of India, for enabling
Indian  participation in the SKA.

\section*{References}

redpajama_set_name: RedPajamaArXiv


text:
Terri Goldson
Health, Education, Welfare, politics, news, faith & information…
Schools Aren't Going to Reopen This Fall – The Atlantic
Date: August 2, 2020Author: Terri D. Goldson, Sr
Published by The Atlantic written by Adrienne LaFrance
In March, we were all living in 15-day increments. Working from home and distance learning, for those who had the terrible luxury of such things, would be a weeks-long affair, surreal but temporary. Fifteen days to flatten the curve. Fifteen days to slow the spread.
Scientists warned us even then that a return to normalcy would take longer, but the telescoped timeline had obvious appeal. You can put up with almost anything for just 15 days.
Acting on the chance to get it right was essential, but we now know it was not temporary. We've seen the failures—in testing, in containment, in federal and state leadership—compound in catastrophic ways. And as our pandemic summer has stretched on, many of us have let go, one by one, of experiences from the world we used to inhabit. We bid goodbye to sleepaway camp, to live music, to distant travel, to boisterous weddings, and to spontaneity in general. Today, a new realization is dawning, and as the debate over schools reopening rages, we must acknowledge it plainly: We aren't going back to how it was. And we shouldn't.
Hotez has good reason to be pessimistic. There were 68,605 new cases in the United States yesterday, according to data from the Centers for Disease Control and Prevention. The seven-day average has stayed above 60,000 new cases per day since July 13. Reaching 100,000 cases per day, once seen as an apocalyptic, worst-case-scenario warning from Anthony Fauci, is no longer difficult to imagine. Indeed, my conversations with epidemiologists in recent days were all strikingly dark. They agreed: Schools should not risk reopening, probably not even for the youngest children, in the coming weeks. "We can't pretend like everything's fine," said Gary Simon, the director of the infectious diseases division at George Washington University. "If I had a school-age kid, I wouldn't want to send him to school."
"This push to open schools is guaranteed to fail," says Peter Hotez, a pediatrician and molecular virologist, and the dean for the National School of Tropical Medicine at Baylor College of Medicine. I've been corresponding with Hotez, and with several epidemiologists, over the course of the pandemic, and have noticed a starkness in their views in recent weeks. "The social-distancing expectations and mask requirements for the lower grades are unrealistic," Hotez told me. "In communities with high transmission, it's inevitable that COVID-19 will enter the schools. Within two weeks of opening schools in communities with high virus transmission, teachers will become ill. All it will take is for a single teacher to become hospitalized with COVID and everything will shut down."
The evidence is all around us. There is the summer camp in Georgia where hundreds of kids and counselors—nearly half the camp—got infected after only a few days together. Then there's the school in Indiana where, just hours after reopening last week, a student tested positive for the coronavirus. ("We knew it was a when, not if," the superintendent told The New York Times, but officials were "very shocked it was on Day 1.")
There's also the JAMA Pediatrics study that suggests that babies and young children can carry extremely high viral loads of SARS-CoV-2. The study's authors found at least as much viral material in the throats and airways of young children as in infected adults, and sometimes 100 times as much as in adults. We've long known that kids older than age 10 can efficiently transmit the virus, but this new research suggests that younger kids pose a risk of transmission to the people around them, just as older children do. The more we learn, the more likely it seems that children are highly effective vectors for transmission. Springtime school closures took place before the virus seized the nation. A return to the classroom now—even with thoughtful precautions—would create excellent conditions to test just how quickly COVID-19 can saturate a community. School was deemed unsafe for children, teachers, and staffers back in March. The pandemic is worse in the United States now than it was then, with multiple epicenters burning across the country. So why would schools reopen now?
"The problem is the White House and the task force could never organize themselves to lead a federal response and bring virus transmission down to containment levels," said Hotez, who has argued for the necessity of a federal containment plan that, if executed effectively, might allow the nation to reopen comprehensively as soon as October. "Instead they took a lazy and careless route, claiming schools are important, as we all know, and the teachers and principals need to figure it out. What they did was deliberately set up the teachers, staff, and parents to fail. It's one of the most careless, incompetent, and heartless actions I've ever seen promoted by the executive branch of the federal government."
For the full story: Click on the link below and read the article by The Atlantic and author Andrienne LaFrance
https://www.theatlantic.com/ideas/archive/2020/08/push-reopen-schools-fail/614869/
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Published by Terri D. Goldson, Sr
Experienced Elementary, Middle & High School Administrator, Consultant, Supervisor and Adjunct Professor at Bowie State University former Adjunct Professor at Southern Conn. State University, Principal of Award Winning Elementary School for closing the Achievement Gap & U.S. News & Report Award winning High School, Provides professional development and motivational presentations. Vice Chairman of Economic Development for the City of Ansonia, Ct.	View all posts by Terri D. Goldson, Sr
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redpajama_set_name: RedPajamaCommonCrawl


Sometimes things go really well throughout the day. You reach closing time and you realize that there weren't too many problems throughout the day. This is rare, but it happens. Two days ago was not one of these days, but it's funny to look back on now.
It's amazing how comedic life can feel on this island, and the events that occur seem to be almost episodic. Two days ago, the episode involved three residents who weren't keen on following some of the Hub rules, so we ended up in a bit of a predicament.
Our rules clearly state that, if you want to be transported to and from the Hub from the Hotspot, you need to attend class. We don't drive our vans like a taxi, if you use our vehicles you need to come to class and then we will transport you back to the camp.
Two days ago, three men rode in the vans to the school, did not attend a class, and then tried to board the vans again and get a ride back to the camp. The driver of the van informed them that they had not attended class, so they would not be allowed to ride back to the camp. They didn't like hearing this, so they climbed into the van and sat in the back row, refusing to move.
This is how we ended up in a good old fashioned stand off. As a teacher in the mornings, I don't have to worry about driving until the afternoon shift begins, but since I had just finished teaching my last class, I watched the situation unfold from the classroom window. It seems that, whenever there is a problem, a group of men tend to just magically appear out of thin air and literally surround the situation. This is a little annoying because it becomes impossible to discretely solve small issues, but sometimes it's encouraging because most of the men who circle-up are doing so in defense of the volunteers and the school.
This issue happens relatively frequently. People think that they can out smart our check-in system or they think that we'll get soft and just drive them back to the camp. But we try not to do this, we try to keep the rules strict in an attempt to keep the system working. This particular situation was weird because usually when people refuse to get out of the van they back down within five minutes or so, but not this time. The stand off just stretched on and on and on. I watched as multiple volunteers made their way over to the van doors to try their luck at coaxing the three men out of the back seat. Then other residents tried as well, along with volunteers standing next to them to assert their authority. Translating didn't work either, as none of the three men understand much English.
So, the drama continued to drag on. Eventually, although I suspected giving more attention to the situation would not work, I took a shot at trying to defuse it. I climbed into the middle seat of the van as everyone else dispersed and the four of us did our best to have an honest conversation. They speak just a little English and, at this point, I speak a little Arabic, so we pasted together a really messy, beautiful string of broken conversation. One of the men in particular is a very sweet guy, so I was really surprised that he was causing such a problem. I did my best to reason with him. He has come to my classes before and I think we have a good rapport with one another.
My attempt was ultimately unsuccessful, although I did manage to get one of them out of the van while the other two stayed put, and the one who got out with me was only stepping out to smoke a cigarette, then he got back in. Looking back on it, it's pretty funny that he was respectful enough not to smoke in the van, but he wasn't respectful enough of everyone else's time. By sitting in the van, we were unable to use the van to transport people to and from the Hotspot, so they were really inconveniencing everyone's day. Alas, we still made everything work, but the situation was all too dramatic.
While I was in the van, they kept telling me that they were going to sleep in the van, continuing their stand off throughout the night. I tried to imagine what this would look like in my head. It's a 25 minute walk back to the Hotspot, why wouldn't they just give it a rest and walk back in the sunshine? The answer? Pride.
Even though we don't fully speak each other's languages, it was perfectly communicated to me that they were sorry, they loved me and the people that work at the Hub, and they didn't want to cause a problem; however, they weren't moving. This, to me, meant simply that they were too prideful to admit they were in the wrong.
As soon as everyone stopped paying them any mind, they got bored, called a cab, and went back to the camp on their own accord. No harm done. They spent a total of 2 hours and 15 minutes waiting for us to cave in and drive them back to the camp. We didn't give in. Rules are rules. What a stupid way to spend an afternoon.
I've been writing this edition of Refugee Trail in my mind for two weeks at this point, but I just keep scribbling down a few sentences and then putting it away. It's now nearly mid-April and I haven't sent out an update from all of the happenings in March. It hit me yesterday evening though, as I was thinking about how late I was on this post, that I don't need to do a full breakdown of everything that happened over the course of 31 days. I was going to talk about the changes in the weather, some specific details about what's been happening with the refugees and all of the goings on at school, but…I won't.
Instead, I just want to babble for a little bit, because the entirety of this experience can be summed up in a few sentences, really.
I'm a veteran volunteer now on this island. I've been here for 5 months and have totaled 8 months with Echo since 2018 began. Dozens of volunteers have rotated in and out since my arrival and 5 of us have stuck around since before the Christmas holiday. Some of us are starting to feel the timeline. There are multiple benefits to this, but there are small negative things that we're noticing too.
For example, one of my long-term comrades recently went away for the weekend, off of the island. When she came back, she said she realized she was talking in circles to the people around her. She just kept saying the same things over and over and over again. She needed to leave the island to get this perspective, but when she brought it back to me and told me this morning about what she had noticed, I couldn't help but agree completely with her. Of course we talk about the same things over and over again, because we're experiencing the same things over and over again. We see and deal with trauma everyday that is being brought directly to us by people who have fled war and torture and corruption and human greed. And, because we need our school/community center to operate correctly, we try to follow a certain number of rules and guidelines.
This takes up a lot of brain space and time. How do you create a safe, welcoming place for people who are dealing with past and current traumas and difficult situations while still trying to run a school? And that's it. Our thoughts spin and spin in the same direction. We say the same things, we're caught in the same routine and the same scenarios. Even still, just this morning, I was walking from my home to the school and experiencing the strange feeling of knowing how perfect the moment was, but not feeling the perfection. I love the work that I do everyday, the weather is perfect, the people I'm around are totally special, and this is a place I've worked hard to be able to call home for this period of time. The only hiccup is my bogged down thoughts, which leave me spinning in circles.
The asylum process is tedious and confusing, I still don't understand why certain things happen and do not happen in reference to individual cases. This is the thing that looms over all of my students, so my lack of understanding is frustrating. I've watched people I interact with and love with everyday get deported, thrown in jail, refused basic human rights, get beaten by the police, get forced off of the island against their will, get forced to remain on the island against their will, and, perhaps worst of all, just generally suffer under the over-crowded conditions of the camp that they live in. My mind gets caught in this weird place between wanting to just hug everyone all of the time and seeing the great benefit to strictly following the rules and making sure the school stays in working order, because structure is good.
I realize after writing this that I don't even know what I'm trying to say with this post. Maybe I just don't feel the need to recap my month because everything seems to be spinning in the same direction that it always has been. I don't know.
Winter has retreated and spring is in full swing here on the island, with temperature regularly between 14 and 17 degrees Celsius throughout the month. It's also been considerably less rainy and the power hasn't gone out half as much as it did in January. It's a relief to be heading into better weather, not to mention the addition of Daylight Savings Time has made it so there is light in the sky as late as 8:00, which I'm really grateful for. With nicer whether; however, comes the fear that more boats will be making their way from Turkey to Greece as the seas are calmer and the chances of encountering environmental problems become slimmer. This means more people are risking there lives and this year has already proven to be a deadly one with many refugees drowning in the waters when they attempt the crossing.
In the evenings these days, when I have the time, I've found myself becoming increasingly curious about things that are happening in the greater world beyond Leros. More nights than not this past week, I've fallen asleep to youtube videos and clips about Brexit, Nancy Pelosi, or the growing field of Democratic Candidates announcing their bid for the presidency of the United States. My brain almost instantly goes numb while listening to these topics; however, I've been feeling the need to stay informed for some reason, despite the small life I am living on this island. Politics matter here, too.
Today was, yet again, a Greek holiday and so the Hub was closed and I had the day to my disposal. I went for a hike with two of my local friends up a long winding dirt road that ends at the edge of the island at a lighthouse that overlooks the harbor. We sat out there for an hour or so in the shade and admired the shimmering sunshine on the perfect blue water of the Mediterranean. The sea is a nice reminder of how small we all are. My cheeks are a bit sun kissed now, a nice reminder of the encroaching summer months.
One of the residents (more importantly, one of my friends) recently moved out of the Hotspot and began renting his own flat just outside of town. He sent me this picture from his veranda to show me the view he has to enjoy everyday. He overlooks the entirety of the town and has a sea view along with a panoramic view of Leros' mountains. Ironically, his home has a view so expansive that he can see the Hotspot where he used to live on the other side of the water, especially in the night hours when the lights are on in the camp. He can literally look down upon the place he dreaded living in for months. Fortunately, he says the tranquility of being outside of town is benefitting his mental state and the clear night skies are keeping him happy when the stars are out.
While setting out for today's hike, I passed by the rare sight of the ferry in the harbor during the daylight hours (it normally arrives and departs at night). Due to weather, the ship was delayed the previous day, so I got the opportunity to snap this picture of it as it headed out to sea. Unfortunately, I found out too late that my friend was on this ship, being transferred to a prison on a different island. This is the same friend who I've written about in previous posts, one who I visited in Leros' jail two times. Last week was the last time I was able to go and see him, I thought things were looking up for him, that he would be able to reapply for asylum and be allowed to stick around, but I heard the news this morning that he was taken away in handcuffs and has been transported to a different island. One of my fellow volunteers heard speculation that too many people were in support of him and trying to help him out that he ended up getting transferred to avoid him getting any assistance. This breaks my heart to think about, but it makes sense. There is no direct ferry from Leros to the island that they sent him to. I can't go and visit him. He's just gone.
And that's the end of this long weekend. School resumes tomorrow and I will officially be graduating more than 20 of my students from the lowest level English class up to the next level. I'm excited to see how things go for them as they transition to this higher level. If things go well, I think it will be one of my more proud teacher moments since arriving on this island.
There seem to be no less than a hundred holidays in Greece throughout the year, but March is perhaps the most holiday-filled. There were two holidays last week, one of which was in celebration of a multiple islands off the coast of Turkey coming back into the possession of Greece many decades ago. To commemorate this occasion, the local Greeks of Leros celebrate with a parade, which somewhat resembles Halloween in the United States. Each group in the parade dressed up in different costumes and then paraded down the streets of Lakki.
Our coordinators decided we should be part of the parade and dress as Greek Gods. I found this comical since none of us are actually from Greece, but I think that was the whole point. So, in the middle of the afternoon on Sunday, the entire group of volunteers and a few dozen residents of the camp dressed in white and spray painted some leaves gold to make into crowns for our heads. When it was all said and done, I think we looked pretty ridiculous–which was perfect. None of us resembled Gods, in my opinion, but we did all at least match.
Me and Mohammed in Greek God attire.
It took a number of hours to prepare everyone's costumes and to dress our van up for the occasion. I think getting ready for the event was the best part, that's when everyone was having the most fun. When it came time for the parade itself, we had to wait over an hour before processing down the main street of Lakki. I attribute the holdup to the Greek culture, nothing ever "needs" to begin on time. But the day was perfect. The sun was out and the temperature was right where it needed to be for a stroll outdoors in strange attire.
Waiting for our turn in the parade.
Our spot in the parade was between a group of women dressed up like flamingoes and a truck full of men sitting in the back of the pickup, dressed like they were going to rob a bank with masks over their faces and plastic guns in their hands. The local elementary school had all of its students dressed up like the different countries of the world. This meant there were a bunch of little tikes running around with giant pieces of paper draped over their shoulders with little sketches of maps on them.
The Echo van, all decked out in Greek God garb.
I think the entire celebration lasted a few hours, but by the time the parade wrapped up we had been preparing for so long that we basically just dispersed and called it a day.
The only hiccup we experienced throughout the day was in the middle of the parade when an on-looker shouted something at our group as we walked by. We made no effort to hide who we were. We were clearly a group of international volunteers and refugees from all over the world. We were not locals. One of the volunteers, who happens to be Greek, overheard one of the spectators shouting something rude at us. I watched as she pulled herself out of the parade and confronted the person in the crowd. When I caught back up with her later, she was upset, but she didn't give me any specifics on what she had said to them or what they had said to her. I already knew the entire story though, just by looking at her face as she stepped out of the parade and feeling her reaction afterwards.
The day was fun. It pulled many of the residents away from the dire conditions of the camp for a while. It's too bad that someone was rude to us, but no one was impacted by it since no one understands Greek and there were many cheers from the crowd to overpower the racism. But, this is the reality, nonetheless.
People tend to disappear on this island. They're here one day and gone the next. Sometimes it's because they've quietly boarded the ferry the evening before and sometimes it's because they've been taken to prison. With volunteers and locals, it's different, obviously. But for the refugees, if you can't locate someone that you're used to seeing, it could be for a variety of reasons. Sometimes, they've snuck onto the ferry and are illegally making their way to Athens, sometimes they've been granted asylum and their travel restrictions have been lifted so they leave the island right away, and sometimes, most horribly, they've been arrested.
Arrests are a unique thing on this island. There is no prison here, just a holding cell at the police station on the other side of the island. The closest prison is on the island of Kos, which is a few hours away by ferry. So, a lot of time when someone seems to vanish, they're just being held in a cell on the other side of the island. In my first three month stint on Leros, I wasn't aware of anyone being put in the jail, but when I left, some of the people I knew the best were arrested and I didn't hear from them for the duration of their time there. One friend spent more than a month in the jail before he was released.
This time around, it's one of the residence who happily greets me every time I see him, who hugs me whenever he can, who has been thrown in jail.
The answer: I don't know. I just really, really do not know.
In an effort to get asylum in Greece, many refugees go through the entire process, often for more than a year. Their cases are accepted or denied, they can get lawyers and appeal their decisions, etc. The process really seems to stretch on and on, but there almost always seems to be something else that can be done other than getting deported back to their home country or to Turkey. Things happen, but the system is so slow that the effect of the cause tends to take time. So, even if someone's case is over and they need to be deported, the slow Greek system may not actually have them sent back to their country for a month or two after the decision is made. This is partly why things can appear to happen so suddenly.
So, my buddy is in jail right now. He might need to be transferred to Kos at some point, but for now he's still on Leros. I went to visit him yesterday. I was told the visiting hours were from 6 to 7, so I went to the store, bought some food, and headed over to the other side of the island. Fortunately, I was able to borrow one of the vehicles I have for work, otherwise I would have had to make the walk over which would have taken about an hour or so. When I parked the car next to the marina, the sunset was bursting in golden rays. The entire island seemed to be glowing, with the sun bouncing off of the white buildings of the hilly town and the mountain behind me. I'm again reminded that the stark beauty of this island means nothing when it comes to the secrets this place can hold. I quickly snapped a photo with my phone out of irony as I climbed from the car. This place is utterly stunning, but haunting as well, as I made my way to the police station to see my captive friend.
Confused, I looked through the metal bars and called out my friends name, but, so not to let the officer be aware of what I was saying, I called out a few words in Farsi. I thought by doing this, I'd be taking a little of the power from the police officer. I heard my words echo off of the bare walls of the cell I was calling into. A moment of nothing, then my friend appeared around the corner. He was dressed how he always is, in his jeans and a jacket, with a lit cigarette in hand.
The police officer rifled through the bag I brought as I greeted my friend at the gate. You're not suppose to touch the prisoners, but I did anyway. I'm used to hugging him whenever I see him, so touching his hand through the bars seemed like nothing. Item by item, the officer passed everything I brought through the bars to my friend. Some peanuts for protein, some dried fruit for vitamins, a can of Coke for comfort because it was still cold, and some potato chips for a snack. 5 sudoku books, something I thought would be useful in keeping his brain active while sitting in the endless boredom, but the pen I brought was not allowed. I hoped I had my basis covered. Other visitors had told me that they had already brought him snacks and hygiene products, because the cell is notorious for its lack-of-care. Prisoners get put in the cell and ignored, they aren't given items to bathe themselves or fed three times a day.
When the officer was finished handing everything through the bars, he took a single step back and said, "you have one minute." He hovered over my shoulder the entire time, so I was actually happy to only have one minute because I realized I didn't have anything to say to my friend if someone else was going to be eavesdropping on the conversation the entire time. Had we been alone, I would have been fine to continue speaking, but not while being watched so closely. It seemed, that after two days in the jail cell, my friend seemed to be doing fine, but it was obvious that the situation could quickly become mentally dire. I hope his lawyer figures something out for him soon.
Now I've seen one more piece of this experience. Now I know a little bit more of the story. Slowly, slowly this whole tale is told.
Babe, you're glowing gold, but I can see you've got a secret.
This is me, prepping for a driving shift while glancing at a phone that isn't mine.
One of the refugees recently moved out of the Hotspot camp and into his own flat in town. His card was "opened", meaning that his documentation was allowing him to travel to mainland Greece. He was due to be transferred by the authorities to a different camp on the Greek mainland, but since he has been on Leros for so many months, he wanted to remain here. He has become comfortable in this little community, he knows some of the locals, he frequents the Hub and has become a friend of many of us volunteers, and the residents at Hotspot know him. So, he has community here. Why would he want to leave just to have to wait for asylum in a new spot in Greece?
By taking a flat, he's removed himself from the difficulties of living in the camp, and also granted himself the opportunity to remain on Leros without any issue. Unfortunately, it's not like all of the problems that a refugee encounters each day simply go away just because they've found themselves a home. For example, when moving into his home, the place didn't have any Wifi, so he and his landlord went to the local phone store to arrange a hookup for him. When the clerk asked him for his tax number, he didn't have one, since he isn't a resident of Greece. His landlord, standing beside him, laughed at him and told him, "see, you are nothing" and preceded to give the clerk his tax number to arrange for the internet to be setup.
The situation was clearly awkward, especially since it was taking place publicly, but my friend, fortunately, had the drive and persistence to standup for himself. It ended with his landlord trying to tell him that he was making a joke, but he stood his ground, making sure that the man understood that jokes like that hit way too close to home and aren't amusing. I was both proud and saddened to hear about how the situation had gone down.
Sometimes, okay, most of the time, when I think about humanity, I think about how sterile we've become. In general, as a species, I think technology has put us on the fast track to disaster. We're not there yet, but we're heading there. We spend way too much time on our phones, glancing at text messages, reading e-mails, and getting distracted by the constant beeping and buzzing of our devices.
This is why moments like this strike such an unusual, unexpected chord in me when they happen. This man, who has just pulled himself away from an amount of agony that no human being should ever have to consistently endure, is only thinking about other people as he walks away. To put this in perspective, I would imagine myself running away from the situation, arms thrown high up into the air, in glee. This kind of thing, the way my friend reacted to his exit, makes me have to take a deep breath for a moment while my brain recalibrates what I'm feeling. How unique to hear about someone truly putting others before himself, losing sleep in his ocean of empathy for his fellow humans.
I want to be more like this guy.