Default SOOP duration: 1 day
Pointing requirements: Off-pointing
Robert Cameron (Proposed), M. Roth, Ground based counterpart.
The scientific aim is to characterize the properties of waves in the photosphere and their coupling with the atmosphere.
Waves are one clear mechanism for transferring energy from the photosphere to the chromosphere and corona. Measuring the properties of the waves requires, in part, a determination of the velocity field. The line-of-sight velocity component can be determined at different heights in the atmosphere by observing Doppler shifts in different spectral lines. From the earth’s vantage point we have high resolution ground based, balloon borne, and satellite instruments. Determining the horizontal velocity has previously relied on using correlation tracking of intensity variations and rely on the questionable assumption that the changes in location of the brightness fluctuations reflect the actual velocity. The orbit and capability to measure Doppler velocities, in conjunction with existing and upcoming ground-based or near-earth observatories, offers the unique chance to directly measure two components of the velocity field using the Doppler effect.
High resolution co-temporal measurements including Doppler velocity maps from SO as well as ground and NEOs are required. In particular the ground-based and NEOs should include high resolution Doppler images in the same line (with a higher cadence than that of SO), as well as lines sampling different heights of the atmosphere. Co-observation with IRIS would be desirable. During the observing period the earth-Sun-SO angle should be between 30? and 60? – a range which represents a compromise between determining the two components of the velocity field and allowing magnetic features which can act as wave guides to be partially resolved.
For ease of understanding the connection between the different heights, the observations would best be performed at the centre of the disk as observed from the earth (where observations over different wavelengths are possible). Because also the achievable cadence will be higher on ground than with SO/PHI, it is preferable to select targets which are closer to the disk centre as seen from earth and at higher heliocentric angles as seen from SO. The highest possible cadence is desirable, and a shorter time series (of down to 30 minutes of Solar orbiter observations) would still allow the scientific objectives to be met. (The ground based and NEO should be made for a period of 90 minutes centred on the 30 minute SO observations). However, in order to guarantee reliable conditions (seeing) at the coordinating ground-based observing facility (e.g. DKIST) a continuous high-cadence observation period of several hours is required.
High resolution context magnetic maps from solar-orbiter immediately before and after the 30 minute observing window are required to provide context and aid co-alignment.
A second observational campaign of an area 45? from disk centre, with a earth-Sun-SO angle of 90?, would be desirable.
|PHI||PHI_nominal_HRT_0 (HRT)||full FoV 1 min cadence, 2 quantities plus magnetic field context|
|EUV & LYA Quiet Sun modes (Q)||Full FoV 1-10s cadence (Just lyman alpha?)|
(e.g., orbital requirements, solar cycle phase, quadrature ...)
|1.2.1 What mechanisms heat the corona?||see text above||several hours, best 30 minutes downlinked||What is the max heliocentric distance that will give the required spatial resolution?||co-observations with NEO at 30, 60, 90 degrees.|
|188.8.131.52 Energy flux in the lower atmosphere||see text above||several hours, best 30 minutes downlinked||What is the max heliocentric distance that will give the required spatial resolution?||co-observations with NEO at 30, 60, 90 degrees.|
184.108.40.206 Two components of velocity. What is the relationship between the components of the velocities in granulation? Supergranulation? Various modes in quiet Sun? (stereoscopic helioseismology)
|Quiet Sun||several hours||What is the max heliocentric distance that will give the required spatial resolution?||co-observations with NEO at ~30º.||Earth/near-Earth assets assumed to be continuously observing (HMI, GONG network, etc.). If not, then co-ordination will need to be taken into consideration.|