In this week's episode, "The Electric Boy" (video preview), narrator Neil deGrasse Tyson shows that without a magnetic field the rate of mutation amongst Earth's living organisms would increase significantly. New evidence for the existence of Earth’s magnetic field has pushed its age back about 250 million years, suggesting that the planet’s earliest life was shielded from the sun’s most harmful cosmic radiation.
"With a weak magnetosphere and a rapid-rotating young Sun, the Earth was likely receiving as many solar protons on an average day as we get today during a severe solar storm," says John Tarduno, a geophysicist at the University of Rochester and lead author of the study.
"That means the particles streaming out of the Sun were much more likely to reach Earth. It's very likely the solar wind was removing volatile molecules, like hydrogen, from the atmosphere at a much greater rate than we're losing them today."
Tarduno says the loss of hydrogen implies a loss of water as well, meaning there may be much less water on Earth today than in its infancy.
To find the strength of the ancient magnetic field, Tarduno and his colleagues from the University of KwaZulu-Natal visited sites in Africa that were known to contain rocks in excess of 3 billion years of age. Not just any rocks of that age would do, however. Certain igneous rocks called dacites contain small millimeter-sized quartz crystals, which in turn have tiny nanometer-sized magnetic inclusions. The magnetization of these inclusions act as minute compasses, locking in a record of the Earth's magnetic field as the dacite cooled from molten magma to hard rock.
Simply finding rocks of this age is difficult enough, but such rocks have also witnessed billions of years of geological activity that could have reheated them and possibly changed their initial magnetic record. To reduce the chance of this contamination, Tarduno picked out the best preserved grains of quartz out of 3.5 billion-year-old dacite outcroppings in South Africa.
Complicating the search for the right rocks further, the effect of the solar wind interacting with the atmosphere can induce a magnetic field of its own, so even if Tarduno did find a rock that had not been altered in 3.5 billion years, he had to make sure the magnetic record it contained was generated by the Earth's core and not induced by the solar wind.
Once he isolated the ideal crystals, Tarduno used a device called a superconducting quantum interface device, or SQUID magnetometer, which is normally used to troubleshoot computer chips because it's extremely sensitive to the smallest magnetic fields. Tarduno pioneered the use of single crystal analysis using SQUID magnetometers. However, for this study, even standard SQUID magnetometers lacked the sensitivity. Tarduno was able to employ a new magnetometer, which has sensors closer to the sample than in previous instruments.
Using the new magnetometer, Tarduno, Research Scientist Rory Cottrell, and University of Rochester students were able to confirm that the 3.5 billion-year-old silicate crystals had recorded a field much too strong to be induced by the solar wind-atmosphere interaction, and so must have been generated by Earth's core.
"We gained a pretty solid idea of how strong Earth's field was at that time, but we knew that was only half the picture," says Tarduno. "We needed to understand how much solar wind that magnetic field was deflecting because that would tell us what was probably happening to Earth's atmosphere."
The solar wind can strip away a planet's atmosphere and bathe its surface in lethal radiation. Tarduno points to Mars as an example of a planet that likely lost its magnetosphere early in its history, letting the bombardment of solar wind slowly erode its atmosphere. To discover what kind of solar wind the Earth had to contend with, Tarduno employed the help of Eric Mamajek, assistant professor of physics and astronomy at the University of Rochester.
"We estimate the solar wind at that time was a couple of orders of magnitude stronger," says Mamajek. "With Earth's weaker magnetosphere, the standoff point between the two was probably less than five Earth radii. That's less than half of the distance of 10.7 radii it is today."
Tarduno says that in addition to the smaller magnetopause allowing the solar wind to strip away more water vapor from the early Earth, the skies might have been filled with more polar aurora. The Earth's magnetic field bends toward vertical at the poles and channels the solar wind toward the Earth's surface there. When the solar wind strikes the atmosphere, it releases photons that appear as shifting patterns of light at night.
With the weakened magnetosphere, the area where the solar wind is channeled toward the surface—an area called the magnetic polar cap—would have been three times larger than it is today, says Tarduno.
"On a normal night 3.5 billion years ago you'd probably see the aurora as far south as New York," says Tarduno.
Earth's Liquid Core --Source of the Magnetic Field
Surprisingly, we know very little about what lies beneath the Earth's surface. The scientific community is in generaly agreement that the world beneath our feet is made up of four layers: a rocky outer crust, a mantle of hot viscous rock, a liquid outer core, the seat of magnetism, and a solid, spinning inner core.
The liquid core, creates the Earth's magnetic field in concert with the spinning solid core, which acts like an electrical motor, reverses itself about 200 times in the last 100 million years. But we don't have the slightest idea why; it's one of the great unsolved mysteries of science.
The Earth's solid inner core is hotter than 1043 K, the Curie point temperature at which the orientations of spins within iron become randomized. Such randomization causes the substance to lose its magnetic field. Therefore the Earth's magnetic field is caused not by magnetized iron deposits, but mostly by electric currents in the liquid outer core.
It is thought that we might be going through a reversal of the magnetic field now. Recorded measurements show that it has diminished as much as six percent in the last century alone, which along with global warming spells potential trouble for the planet. The Earth's magnetic field deflects dangerous cosmic rays away from the planet's surface into two zones of near space called the Van Allen belts.
Mars Missing Magnetic Field -Was It Destroyed by a Massive Asteroid Impact?
Scientists think the Martian magnetic field might have been hammered into submission by strikes from space. Planetary magnetic fields are created by massive molten metal currents within the planet's core. A flowing current creates a magnetic field, even when the current is massive volumes of charged liquid metal moving under the influence of temperature gradients (convection) - in fact, especially then. But magnetic analysis of Martian sites by Berkeley researchers show that the red planet's protective field was switched off half a billion years ago, and now some scientists say they know why.
All was pure speculation until data came back from the Mars Global Surveyor and other recent spacecraft. In 2009, planetary scientists Robert Lillis and Michael Manga, both of the University of California, Berkeley, linked age estimates of impact basins with magnetic field strength to show that the previously established date of heavy bombardment, about 3.9 billion years ago, corresponds to the death of Mars's dynamo.
Lillis, Manga, and planetary geophysicist James Roberts of John Hopkins University Applied Physics lab in Laurel, Maryland, modeled the effects of heat produced by impacts and calculated that a period of massive asteroid impacts, known to have happened around the same time, could not only have massively impacted on the surface Deep Impact-style (with all the atmospheric alteration and great-big-crater-making that entails) but added enough energy to the planet to heat up the outer layers of the planet.
Without the huge temperature difference between the core and mantle, the mega-magnetic dynamo convection currents would be switched off - and unable to start up again when things cooled down. Remember, planetary core behavior is still carrying on from when the planets first formed - as far as they're concerned the whole "crust" thing and all life as we know it is just a cooling scum on the surface. If you break something from back then you just don't have the juice to start it up again.
Without the magnetic field Mars is defenseless against the radiation that constantly pours in from space. Earth is thought to have survived the same space-bombing because of our superior size, with our dynamo maybe stuttering a little but - very importantly - not stopping. As you can maybe tell by the fact you exist.
Cosmic-Scale Magnetic Fields
The mention of cosmic-scale magnetic fields is still likely to met with an uncomfortable silence in some astronomical circles – and after a bit of foot-shuffling and throat-clearing, the discussion will be moved on to safer topics. But look, they’re out there. They probably do play a role in galaxy evolution, if not galaxy formation – and are certainly a feature of the interstellar medium and the intergalactic medium.
It is expected that the next generation of radio telescopes, such as LOFAR (Low Frequency Array) and the SKA (Square Kilometre Array), will make it possible to map these fields in unprecedented detail – so even if it turns out that cosmic magnetic fields only play a trivial role in large-scale cosmology – it’s at least worth having a look.
At the stellar level, magnetic fields play a key role in star formation, by enabling a protostar to unload angular momentum. Essentially, the protostar’s spin is slowed by magnetic drag against the surrounding accretion disk – which allows the protostar to keep drawing in more mass without spinning itself apart.
At the galactic level, accretion disks around stellar-sized black holes create jets that inject hot ionised material into the interstellar medium – while central supermassive black holes may create jets that inject such material into the intergalactic medium.
The image below shows the total radio continuum emission from the "whirlpool" galaxy M51 (distance estimates range between 13 and 30 million light years) is strongest at the inner edges of the optical spiral arms, probably due to the compression of magnetic fields by density waves. Image courtesy of NRAO/AUI.
Within galaxies, ‘seed’ magnetic fields may arise from the turbulent flow of ionised material, perhaps further stirred up by supernova explosions. In disk galaxies, such seed fields may then be further amplified by a dynamo effect arising from being drawn into the rotational flow of the whole galaxy. Such galactic scale magnetic fields are often seen forming spiral patterns across a disk galaxy, as well as showing some vertical structure within a galactic halo.
Similar seed fields may arise in the intergalactic medium – or at least the intracluster medium. It’s not clear whether the great voids between galactic clusters would contain a sufficient density of charged particles to generate significant magnetic fields.
It is anticipated that next generation radio telescopes like the Square Kilometre Array will significantly enhance cosmic magnetic field research.
Seed fields in the intracluster medium might be amplified by a degree of turbulent flow driven by supermassive black hole jets but, in the absence of more data, we might assume that such fields maybe more diffuse and disorganised that those seen within galaxies.
The strength of intracluster magnetic fields averages around 3 x 10-6 gauss (G), which isn’t a lot. The Earth’s magnetic fields averages around 0.5 G and a refrigerator magnet is about 50 G. Nonetheless, these intracluster fields offer the opportunity to trace back past interactions between galaxies or clusters (e.g. collisions or mergers) – and perhaps to determine what role magnetic fields played in the early universe, particularly with respect to the formation of the first stars and galaxies.
Magnetic fields can be indirectly identified through a variety of phenomena:
• Optical light is partly polarised by the presence of dust grains which are drawn into a particular orientation by a magnetic field and then only let through light in a certain plane.
• At a larger scale, Faraday rotation comes into play, where the plane of already polarised light is rotated in the presence of a magnetic field.
• There’s also Zeeman splitting, where spectral lines – which normally identify the presence of elements such as hydrogen – may become split in light that has passed through a magnetic field.
Wide angle or all-sky surveys of synchrotron radiation sources (e.g. pulsars and blazars) allow measurement of a grid of data points, which may undergo Faraday rotation as a result of magnetic fields at the intergalactic or intracluster scale.
Moon Once Harbored a Long-Lived Dynamo" --New MIT Research: Magnetic Field Existed 3.6 Billion Years
MIT's research on an ancient lunar rock suggests that the moon once harbored a long-lived dynamo — a molten, convecting core of liquid metal that generated a strong magnetic field 3.56 billion years ago. The findings point to a dynamo that lasted much longer than scientists previously thought, and suggest that an alternative energy source may have powered the dynamo.
The magnetic field existed until at least 3.56 billion years ago, an MIT study suggests — about 160 million years longer than scientists had thought. “It seems like the lunar dynamo lasted very late in the Moon’s history,” says Benjamin Weiss, a palaeomagnetics expert at the Massachusetts Institute of Technology (MIT) in Cambridge. “That’s a very surprising result.”
“The moon has this protracted history that’s surprising,” says Weiss, an associate professor of planetary science at MIT. “This provides evidence of a fundamentally new way of making a magnetic field in a planet a new power source.”
The paper is the latest piece in a puzzle that planetary scientists have been working out for decades. In 1969, the Apollo 11 mission brought the first lunar rocks back to Earth — souvenirs from Neil Armstrong and Buzz Aldrin’s historic moonwalk. Since then, scientists have probed the rocky remnants for clues to the moon’s history. They soon discovered that many rocks were magnetized, which suggested that the moon was more than a cold, undifferentiated pile of space rubble. Instead, it may have harbored a convecting metallic core that produced a large magnetic field, recorded in the moon’s rocks.
Exactly what powered the dynamo remains a mystery. One possibility is that the lunar dynamo was self-sustaining, like Earth’s: As the planet has cooled, its liquid core has moved in response, sustaining the dynamo and the magnetic field it produces. In the absence of a long-lived heat supply, most planetary bodies will cool within hundreds of millions of years of formation.
A dynamo still exists within Earth because heat, produced by the radioactive decay of elements within the planet, maintains the core’s convection. Models have shown that if a lunar dynamo were powered solely by cooling of the moon’s interior, it would have been able to sustain itself only for a few hundred million years after the moon formed — dissipating by 4.2 billion years ago, at the very latest.
However, Weiss and his colleagues found some surprising evidence in a bit of lunar basalt dubbed 10020. The Apollo 11 astronauts collected the rock at the southwestern edge of the Sea of Tranquility; scientists believe it was likely ejected from deep within the moon 100 million years ago, after a meteor impact. The group confirmed previous work dating the rock at 3.7 billion years old, and found that it was magnetized — a finding that clashes with current dynamo models.
Weiss collaborated with researchers at the University of California at Berkeley and the Berkeley Geochronology Center, who determined the rock’s age using radiometric dating. After a rock forms, a radioactive potassium isotope decays to a stable argon isotope at a known rate. The group measured the ratio of potassium to argon in a small piece of the rock, using this information to ascertain that the rock cooled from magma 3.7 billion years ago.
Weiss and graduate student Erin Shea then measured the rock’s magnetization, and found that the rock was magnetized. However, this didn’t necessarily mean that the rock, and the moon, had a dynamo-generated magnetic field 3.7 billion years ago: Subsequent impacts may have heated the rock and reset its magnetization.
To discard this possibility, the team examined whether the rock experienced any significant heating since its ejection onto the moon’s surface. Again, they looked to isotopes of potassium and argon, finding that the only heating the rock had experienced since it was ejected onto the lunar surface came from simple exposure to the sun’s rays.
“It’s basically been in cold storage for 3.7 billion years, essentially undisturbed,” Weiss says. “It retains a beautiful magnetization record.”
Weiss says the rock’s evidence supports a new mechanism of dynamo generation that was proposed last year by scientists at University of California at Santa Cruz (UCSC). This hypothesis posits that the moon’s dynamo may have been powered by Earth’s gravitational pull. Billions of years ago, the moon was much closer to Earth than it is today; terrestrial gravity may have had a stirring effect within the moon’s core, keeping the liquid metal moving even after the lunar body had cooled.
Francis Nimmo, a professor of earth and planetary sciences at UCSC and one of the researchers who originally put forth the new dynamo theory, says Weiss’ evidence provides scientists with a new picture of the moon’s evolution.
“We generally assume that cooling is the main mechanism for driving a dynamo anywhere,” says Nimmo, who was not involved in the current study. “This lunar data is telling us that other mechanisms may also play a role, not just at the moon, but elsewhere, too.”
Vast Magnetic Fields Ruled the Universe Long Before Stars and Galaxies Formed
Scientists from the California Institute of Technology and UCLA have discovered evidence of "universal ubiquitous magnetic fields" that have permeated deep space between galaxies since the time of the Big Bang. Caltech physicist Shin'ichiro Ando and Alexander Kusenko, a professor of physics and astronomy at UCLA, studied images of the most powerful objects in the universe — supermassive black holes that emit high-energy radiation as they devour stars in distant galaxies — obtained by NASA's Fermi Gamma-ray Space Telescope. "We found the signs of primordial magnetic fields in deep space between galaxies," Ando said.
Physicists have hypothesized for many years that a universal magnetic field should permeate deep space between galaxies, but there was no way to observe it or measure it until now. The physicists produced a composite image of 170 giant black holes and discovered that the images were not as sharp as expected.
"Because space is filled with background radiation left over from the Big Bang, as well as emitted from galaxies, high-energy photons emitted by a distant source can interact with the background photons and convert into electron-positron pairs, which interact in their turn and convert back into a group of photons somewhat later," said Kusenko, who is also a senior scientist at the University of Tokyo's Institute for Physics and Mathematics of the Universe.
"While this process by itself does not blur the image significantly, even a small magnetic field along the way can deflect the electrons and positrons, making the image fuzzy," he said.
From such blurred images, the researchers found that the average magnetic field had a "femto-Gauss" strength, just one-quadrillionth of the Earth's magnetic field. The universal magnetic fields may have formed in the early universe shortly after the Big Bang, long before stars and galaxies formed, Ando and Kusenko said.
Do Primordial Magnetic Fields Roam the Universe?
NASA’s Fermi Gamma-ray Space Telescope may have uncovered a new high energy mystery: galaxies and even large-scale galaxy clusters have magnetic fields shrouding them much like Earth.
While examining distant extra-galactic sources, a team of astronomers at the University of Geneva’s Center for Astrophysics found something startling; distant sources such as blazars and highly energetic galactic nuclei seemed sapped of their predicted strength. This effect is the same without variation in all directions, which suggest that free floating magnetic fields range the cosmos, perhaps predating the modern day galactic fields.
These intervening fields are a predicted cause of the observed drop in gamma-ray energy from these distant sources. Could the universe itself have an overall polarized field? Or is there another effect that has yet to be accounted for, such as intervening dark matter or dark energy? Further analysis by Fermi and other scopes soon to come online may prove to be key to unraveling this mysterious effect.
Another international team of researchers have stared down the barrel of one of the most violently energetic objects in the universe - and they didn't blink. Instead, they've figured out the physics behind one of the most impressive astrophysical events in existence.
BL Lacertae is a blazar, a supermassive galactic-core black hole emitting vast and variable beams of energy. Please understand that giving this thing a name like "blazar" is like calling a speeding sixteen wheeler truck full of professional wrestlers, grizzly bears and dynamite a "gentle prodder." The English language simply lacks the ability to get across the staggering scale of these events - because it doesn't have a case above upper or letters bigger than capital.
The most famous property of black holes is the event horizon, the "point of no return" beyond which you cannot escape. But even before this final barrier you're still close to a gigantic gravitational well built out of most of an Active Galactic Nucleus (AGN) - if not a point of no return, it's still a "point of incredibly difficult to escape from". We observe vast, super-energetic near-light speed particle streams from the poles of some such systems - what gives them the power?
That was the question Professor Alan Marscher and an international team set out to answer, confirming their theories with observations of the inner workings of the BL Lac blazar particle stream. Big questions need big tools (especially when they're over nine hundred million miles away), so they enlisted the help of a global network of satellites including the Very Large Baseline Array (VLBA), a continental set of dishes with resolution equivalent to a dish larger than the USA.
These mega-scale observations tracked particles as they were hurled from the throat of the blazar, emitting radiation as they go, and confirmed the team's theories that the power source is massively compressed and twisted magnetic fields.
As material is sucked into the black hole, it spirals in along a large accretion disk. As it gets closer to being consumed, the material is crushed smaller and smaller by increasing gravitational forces - and the magnetic field lines coming along with it are crushed together as well, creating hugely intense fields oriented around the spinning black hole. These gigantic fields can drive particles away from the hole, causing them to corkscrew along a narrowly confined path while emitting precise bursts of radiation - bursts the astronomers observed exactly.
Understanding these universe-grade events is a great step forward in astrophysics - for one thing, The BL Lacertae blazar is a particle accelerator that makes the LHC look like an asthmatic child throwing pebbles.
"X-Points" --Space Portals Linking Earth to Sun's Magnetic Field
Data from NASA's Polar spacecraft, circa 1998, provided crucial clues to finding "portals" -- an extraordinary opening in space or time that connects travelers to distant realms. "We call them X-points or electron diffusion regions," explains plasma physicist Jack Scudder of the University of Iowa. "They're places where the magnetic field of Earth connects to the magnetic field of the Sun, creating an uninterrupted path leading from our own planet to the sun's atmosphere 93 million miles away."
Observations by NASA's THEMIS spacecraft and Europe's Cluster probes suggest that these magnetic portals open and close dozens of times each day. They're typically located a few tens of thousands of kilometers from Earth where the geomagnetic field meets the onrushing solar wind. Most portals are small and short-lived; others are yawning, vast, and sustained. Tons of energetic particles can flow through the openings, heating Earth's upper atmosphere, sparking geomagnetic storms, and igniting bright polar auroras.
NASA is planning a mission called "MMS," short for Magnetospheric Multiscale Mission, due to launch in 2014, to study the phenomenon. Bristling with energetic particle detectors and magnetic sensors, the four spacecraft of MMS will spread out in Earth's magnetosphere and surround the portals to observe how they work.
Just one problem: Finding them. Magnetic portals are invisible, unstable, and elusive. They open and close without warning "and there are no signposts to guide us in," notes Scudder.* Portals form via the process of magnetic reconnection. Mingling lines of magnetic force from the sun and Earth criss-cross and join to create the openings. "X-points" are where the criss-cross takes place. The sudden joining of magnetic fields can propel jets of charged particles from the X-point, creating an "electron diffusion region."
To learn how to pinpoint these events, Scudder looked at data from a space probe that orbited Earth more than 10 years ago.* "In the late 1990s, NASA's Polar spacecraft spent years in Earth's magnetosphere," explains Scudder, "and it encountered many X-points during its mission."
Because Polar carried sensors similar to those of MMS, Scudder decided to see how an X-point looked to Polar. "Using Polar data, we have found five simple combinations of magnetic field and energetic particle measurements that tell us when we've come across an X-point or an electron diffusion region. A single spacecraft, properly instrumented, can make these measurements."
This means that single member of the MMS constellation using the diagnostics can find a portal and alert other members of the constellation. Mission planners long thought that MMS might have to spend a year or so learning to find portals before it could study them. Scudder's work short cuts the process, allowing MMS to get to work without delay.* It's a shortcut worthy of the best portals of fiction, only this time the portals are real. And with the new "signposts" we know how to find them.
Mapping the Large-scale Magnetic Field of the Milky Way
The interstellar medium of the Milky Way comprises magnetic fields, electrons, atomic gas and other components which affect the polarisation plane of the radio emission. The Partner Group of the Max Planck Institute for Radio Astronomy, which was set up at the National Astronomical Observatory (NAO) in Beijing, investigated the properties of regions of large-scale diffuse emission and mapped the structure of large objects which cannot be observed by larger radio telescopes. These include densely ionised clouds – the HII regions – and the remnants of exploded stars.
The aim of the project was to map the large-scale magnetic field of the Milky Way. The German and Chinese researchers found a handful of peculiar clumps with very strong, regular magnetic fields (Faraday screens) and two new supernova remnants each measuring around one degree. These are the first sources of this type to be discovered with a Chinese radio telescope; astronomers are currently only aware of 270 such objects in the Milky Way. The researchers were also able to classify two incorrectly identified supernova remnants as thermal radio sources.
The new atlas needed more than 4,500 hours of observations to compile, and its angular resolution is similar to that of the 21-cm wavelength survey of the Milky Way obtained at the 100-metre radio telescope at Effelsberg. The comparative analysis of these two large-scale sky surveys at similar angular resolution leads to a better understanding of the processes occurring in the interstellar medium.
The establishment of the Partner Group in China dates back to a resolution of the Max Planck Society on November 9, 2000. The proposal involved collaboration in the exploration of magnetic fields in galaxies with special emphasis being placed on the investigation of the magnetic field of our Milky Way.
The most important contribution made by the Max Planck Institute for Radio Astronomy in Bonn relates to the construction of a receiver for radio emission at six-centimetre wavelength including polarisation, which is being used at the 25-metre Nanshan radio telescope in Urumqi. The advantage of this radio telescope is its location at an altitude of 2,000 metres, where the better weather conditions are advantageous when observing radio emission at higher frequencies.
“Reciprocal visits to the institutes involved have formed a whole series of personal contacts,” says Richard Wielebinski, emeritus Director at the Max Planck Institute for Radio Astronomy. “As far as the German researchers are concerned, we have established a good collaboration with our Chinese colleagues. Things which began with the Partner Group will be continued on a personal level.”
“In the course of our work on this project, a total of five doctorates have been completed in our research group,” says Jin-Lin Han, the Head of the Partner Group in Beijing. “Our collaboration has significantly boosted the development of radio astronomy in China. The way the objective of the Partner Group has been achieved is excellent.”
The results of the research project encompass 24 scientific publications since 2002, most of them in the renowned European journal Astronomy & Astrophysics (A&A). The project has provided researchers with a great deal of experience in conducting radio continuum observations and means significant progress has been made in the construction of receiver systems for Chinese astronomy.
Gigantic Galactic Magnetic Field Extends Far Beyond Our Solar System
Scientists on NASA's Interstellar Boundary Explorer (IBEX) mission, including a team leader from the University of New Hampshire, report that recent, independent measurements have validated one of the mission's signature findings—a mysterious "ribbon" of energy and particles at the edge of our solar system that appears to be a directional "roadmap in the sky" of the local interstellar magnetic field. This enigmatic “ribbon” of energetic particles may be only a small sign of the vast influence of the galactic magnetic field that extends well beyond our solar system.
Unknown until now, the direction of the galactic magnetic field may be a missing key to understanding how the heliosphere—the gigantic bubble that surrounds our solar system—is shaped by the interstellar magnetic field and how it thereby helps shield us from dangerous incoming galactic cosmic rays.
"Using measurements of ultra-high energy cosmic rays on a global scale, we now have a completely different means of verifying that the field directions we derived from IBEX are consistent," says Nathan Schwadron, lead scientist for the IBEX Science Operations Center at the UNH Institute for the Study of Earth, Oceans, and Space. Schwadron and IBEX colleagues published their findings online today in Science Express.
Establishing a consistent local interstellar magnetic field direction using IBEX low-energy neutral atoms and galactic cosmic rays at ten orders of magnitude higher energy levels has wide-ranging implications for the structure of our heliosphere and is an important measurement to be making in tandem with the Voyager 1 spacecraft, which is in the process of passing beyond our heliosphere.
"The cosmic ray data we used represent some of the highest energy radiation we can observe and are at the opposite end of the energy range compared to IBEX's measurements," says Schwadron. "That it's revealing a consistent picture of our neighborhood in the galaxy with what IBEX has revealed gives us vastly more confidence that what we're learning is correct."
How magnetic fields of galaxies order and direct galactic cosmic rays is a crucial component to understanding the environment of our galaxy, which in turn influences the environment of our entire solar system and our own environment here on Earth, including how that played into the evolution of life on our planet.
Notes David McComas, principal investigator of the IBEX mission at Southwest Research Institute and coauthor on the Science Express paper, “We are discovering how the interstellar magnetic field shapes, deforms, and transforms our entire heliosphere."
To date, the only other direct information gathered from the heart of this complex boundary region is from NASA's Voyager satellites. Voyager 1 entered the heliospheric boundary region in 2004, passing beyond what's known as the termination shock where the solar wind abruptly slows. Voyager 1 is believed to have crossed into interstellar space in 2012.
Interestingly, when scientists compared the IBEX and cosmic ray data with Voyager 1's measurements, the Voyager 1 data provide a different direction for the magnetic fields just outside our heliosphere.
That's a puzzle but it doesn't necessarily mean one set of data is wrong and one is right. Voyager 1 is taking measurements directly, gathering data at a specific time and place, while IBEX gathers information averaged over great distances—so there is room for discrepancy. Indeed, the very discrepancy can be used as a clue: understand why there's a difference between the two measurements and gain new insight.
"It's a fascinating time," says Schwadron. "Fifty years ago, we were making the first measurements of the solar wind and understanding the nature of what was just beyond near-Earth space. Now, a whole new realm of science is opening up as we try to understand the physics all the way outside the heliosphere."
The image at the top of the page is a model of the interstellar magnetic fields – which would otherwise be straight — warping around the outside of our heliosphere, based on data from NASA’s Interstellar Boundary Explorer. The red arrow shows the direction in which the solar system moves through the galaxy.
IBEX is a NASA Heliophysics Small Explorer mission. The Southwest Research Institute in San Antonio, Texas, leads IBEX with teams of national and international partners. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for the agency's Science Mission Directorate in Washington.
'Super-Earths' May Lack a Magnetic Field -Exist as Dead Zones
Rocky planets a few times heavier than Earth that were thought might be life-friendly may lack a protective magnetic field that originates from an iron core that is at least partly molten.
A simulation of super-Earths between a few times and 10 times Earth's mass suggests that high pressures will keep the core solid, according to Guillaume Morard of the Institute of Mineralogy and Physics of Condensed Matter in Paris, France. Without a magnetic field, the planets would be bathed in harmful radiation, and their atmospheres would be eroded away by particles streaming from their stars.
The present-day Mars is a prefect example of a planet that lost its magnetic field. Planetary magnetic fields are created by massive molten metal currents within the planet's core. A flowing current creates a magnetic field, even when the current is massive volumes of charged liquid metal moving under the influence of temperature gradients (convection). But magnetic analysis of Martian sites by Berkeley researchers show that the red planet's protective field was switched off half a billion years ago.
Without the magnetic field Mars and perhaps Super Earths in the Milky Way are defenseless against the radiation that constantly pours in from space. Earth is thought to have survived the same space-bombing because of our superior size, with our dynamo maybe stuttering a little but - very importantly - not stopping.
So life would have trouble getting started on super-Earths, even if they lie in the habitable zone around their stars.
However, Vlada Stamankovic of the German Aerospace Center in Berlin reckons it is too soon to rule out molten iron cores - and magnetic fields - for super-Earths. Their interiors might get hot enough to melt iron, he says. "Actual temperatures could be much larger than assumed - we simply do not know."
About 500 exoplanets are now known, but most of these have been hot giants circling too close to their stars, because they are easiest to find. As techniques have been refined, smaller planets have come into view, and a recent survey by University of California astronomers, Andrew Howard and Geoffrey Marcy, concluded that about a quarter of all Sun-like stars should have Earth-size planets.
Analysis of the Kepler Mission "400," may soon reveal Earth-size planets as well as the existence of magnetic fields and the possibility of life-bearing habitats.
Enormous Magnetic Fields of Embryonic Black Holes --"Trigger the Brightest Explosions in the Universe"
t has been speculated for a long time that enormous magnetic field strengths, possibly higher than what has been observed in any known astrophysical system, are a key ingredient in short gamma-ray burst, one of the brightest explosions observed in the universe.Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) have now succeeded in simulating a mechanism which could produce such strong magnetic fields prior to the collapse to a black hole.
Ultra-high magnetic fields -- stronger than ten or hundred million billion times Earth's magnetic field -- are generated from much lower initial neutron star magnetic fields. An ultra-dense ("hypermassive") neutron star is formed when two neutron stars in a binary system finally merge. Its short life ends with the catastrophic collapse to a black hole, possibly powering a short gamma-ray burst, one of the brightest explosions observed in the universe. Short gamma-ray bursts as observed with satellites like XMM Newton, Fermi or Swift release within a second the same amount of energy as our Galaxy in one year.
This could be explained by a phenomenon that can be triggered in a differentially rotating plasma in the presence of magnetic fields: neighbouring plasma layers, which rotate at different speeds, "rub against each other," eventually setting the plasma into turbulent motion. In this process called magnetorotational instability magnetic fields can be strongly amplified. This mechanism is known to play an important role in many astrophysical systems such as accretion disks and core-collapse supernovae. It had been speculated for a long time that magnetohydrodynamic instabilities in the interior of hypermassive neutron stars could bring about the necessary magnetic field amplification. The actual demonstration that this is possible has only now been achieved with the present numerical simulations.
The scientists of the Gravitational Wave Modelling Group at the AEI simulated a hypermassive neutron star with an initially ordered ("poloidal") magnetic field, whose structure is subsequently made more complex by the star's rotation. Since the star is dynamically unstable, it eventually collapses to a black hole surrounded by a cloud of matter, until the latter is swallowed by the black hole.
These simulations have unambiguously shown the presence of an exponentially rapid amplification mechanism in the stellar interior -- the magnetorotational instability. This mechanism has so far remained essentially unexplored under the extreme conditions of ultra-strong gravity as found in the interior of hypermassive neutron stars. This is because the physical conditions in the interior of these stars are extremely challenging.
The discovery is interesting for at least two reasons. First, it shows for the first time unambiguously the development of the magnetorotational instability in the framework of Einstein's theory of general relativity, in which there exist no analytical criteria to date to predict the instability. Second, this discovery can have a profound astrophysical impact, supporting the idea that ultra strong magnetic fields can be the key ingredient in explaining the huge amount of energy released by short gamma-ray bursts.
The NASA image at the top of the page shows a black hole devouring a neutron star. Scientists say they have seen tantalizing, first-time evidence of a black hole eating a neutron star-first stretching the neutron star into a crescent, swallowing it, and then gulping up remnants of the star in the minutes and hours that followed.
Image credits: With thanks to Don Davis, NASA/JPL. ESO