The mystery involves electron acceleration during magnetic explosions that occur, for example, in solar flares and "substorms" in the Earth's magnetosphere - the comet-shaped protective sheath that surrounds the planet and where brilliant auroras occur.
During solar flares, accelerated electrons take away up to 50 percent of the total released flare energy. How so many electrons are accelerated to such high energies during these explosive events in our local part of the universe has remained unexplained.
A mainstream theory holds that the mysterious, fast-moving electrons are primarily accelerated at the magnetic explosion site - called the reconnection layer - where the magnetic fields are annihilated and the magnetic energy is rapidly released. However, physicist Li-Jen Chen of the Space Science Center within the UNH Institute for the Study of Earth, Oceans, and Space discovered that the most powerful electron acceleration occurs in the regions between adjacent reconnection layers, in structures called magnetic islands.
When Chen analyzed 2001 data from the four-spacecraft Cluster satellite mission, which has been studying various aspects of Earth's magnetosphere, she found a series of reconnection layers and islands that were formed due to magnetic reconnection.
"Our research demonstrates for the first time that energetic electrons are found most abundantly at sites of compressed density within islands," reports Chen.
Another recent theory, published in the journal Nature, has suggested that "contracting magnetic islands" provide a mechanism for electron acceleration. While the theory appears relevant, it needs to be developed further and tested by computer simulations and experiments, according to the UNH authors.
Until the UNH discovery there had been no evidence showing any association between energetic electrons and magnetic islands. This lack of data is likely due to the fact that encounters of spacecraft with active magnetic explosion sites are rare and, if they do occur, there is insufficient time resolution of the data to resolve island structures.
In the Nature Physics paper, entitled "Observation of energetic electrons within magnetic islands," lead author Chen reports the first experimental evidence for the one-to-one correspondence between multiple magnetic islands and energetic electron bursts during reconnection in the Earth's magnetosphere.
"Our study is an important step towards solving the mystery of electron acceleration during magnetic reconnection and points out a clear path for future progress to be made," says Chen. UNH collaborators on the paper include Amitava Bhattacharjee, Pamela Puhl-Quinn, Hong-ang Yang, and Naoki Bessho.
Source: University of New Hampshire
Related stories:
Physicists pin down spin of surface atoms
Scientists who dream of shrinking computers to the nanoscale look to atomic spin as one possible building block for both processor and memory, yet setting the spin of an atom, let alone measuring it, has been a challenge.
Disorder May Be in Order for ‘Spintronic’ Devices
Physicists at JILA are using ultrashort pulses of laser light to reveal precisely why some electrons, like ballet dancers, hold their spin positions better than others—work that may help improve spintronic devices, which exploit the magnetism or “spin” of electrons in addition to or instead of their charge. One thing spinning electrons like, it turns out, is some disorder.
Team Finds Magnetic Islands Are Source of Mysterious High Speed Electrons
A team of scientists led by University of Maryland physics professor James Drake appear to have solved a key remaining mystery about how the interaction of magnetic fields produce the explosive releases of energy seen in solar flares, storms in the Earth’s magnetosphere and many other powerful cosmic events.
Electrons discover their individuality
(PhysOrg.com) -- Electrons have something in common with people: the more information they acquire about their setting, the more they become aware of their individuality and the more belonging to a group loses its importance. As a result, the coherent harmony that binds the electrons into a fixed relationship with their environment is lost. This is what scientists at the Fritz-Haber Institute of the Max-Planck Society discovered when, with the aid of X-rays, they catapulted electrons out of molecules consisting of two nitrogen atoms.
Integral locates origin of high-energy emission from Crab Nebula
(PhysOrg.com) -- Thanks to data from ESA's Integral gamma-ray observatory, scientists have been able to locate where particles in the vicinity of the rotating neutron-star in the Crab Nebula are accelerated to immense energies.
Magnetism and Superconductivity Observed to Exist in Harmony
(Physorg.com) -- Physicists at Los Alamos National Laboratory, along with colleagues at institutions in Switzerland and Canada, have observed, for the first time in a single exotic phase, a situation where magnetism and superconductivity are necessary for each other's existence.
Scientists reveal effects of quantum 'traffic jam' in high-temperature superconductors
(PhysOrg.com) -- Scientists at the U.S. Department of Energy's Brookhaven National Laboratory, in collaboration with colleagues at Cornell University, Tokyo University, the University of California, Berkeley, and the University of Colorado, have uncovered the first experimental evidence for why the transition temperature of high-temperature superconductors -- the temperature at which these materials carry electrical current with no resistance -- cannot simply be elevated by increasing the electrons' binding energy. The research -- to be published in the August 28, 2008, issue of
Nature -- demonstrates how, as electron-pair binding energy increases, the electrons' tendency to get caught in a quantum mechanical "traffic jam" overwhelms the interactions needed for the material to act as a superconductor -- a freely flowing fluid of electron pairs.
Air-purifying church windows early nanotechnology
Stained glass windows that are painted with gold purify the air when they are lit up by sunlight, a team of Queensland University of Technology experts have discovered.