Press Release

UM Researchers Uncover Last Major Piece to Puzzle of Massive Magnetic Explosions

By SpaceRef Editor
February 6, 2003
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COLLEGE PARK, Md. – A team of scientists led by University of Maryland
physics professor James Drake has found what may be one of the final
pieces to
a puzzle scientists have been trying to solve for almost forty years: how
magnetic
fields produce the explosive releases of energy seen in solar flares, in
magnetic
storms at the edge of Earth’s atmosphere and in many other powerful cosmic

events throughout the Universe.


Magnetic field, or force, lines act much like giant rubber bands.
Physicists
have long been convinced that the primary mechanism for release of
magnetic energy
is a process called magnetic reconnection that occurs when
oppositely-directed
magnetic field lines come in contact.

During this process, parallel magnetic field lines break and
reconnect, forming
back-to-back slingshots that release their energy by exploding outwards in
opposite
directions. Since charged particles are trapped on magnetic field lines,
most of the
energy in the magnetic field is converted to the flow of ionized particles
(plasma) that is
pulled along by the expanding field lines.

However, classic magnetic reconnection theory has one major problem;
it
incorrectly predicts a gradual release of energy. For example,
theoretical calculations
generally predicted that a solar flare should take years or even decades
to release
energy, while observations have shown it takes only minutes.

In the February 7 edition of the journal Science, Drake and his
colleagues release
findings that for the first time indicate that at least some of this
explosive energy happens as
the result of plasma turbulence generated during reconnection. Using
large-scale computer
simulations developed at Maryland, together with data from NASA’s Polar
satellite, the
team found that intense currents of electrons are generated during
magnetic reconnection.

These intense currents drive strong turbulence that takes the form
of “electron
holes,” three-dimensional regions where the electron density is depleted.
The satellite
data from Polar indicate that the magnetosphere is riddled with these
holes, which have
diameters of up to a mile and travel at speeds in excess of 1000 miles per
second.
According to the researchers, the intense electric field associated with
these electron
holes causes electron scattering that is sufficiently strong to sustain
fast reconnection.

“Electron scattering by the electron holes also strongly heats
electrons and
may therefore ultimately provide an explanation for the surprisingly large
amount of
energy that is transferred to electrons during reconnection events in the
solar corona
and the Earth’s magnetosphere,” said Drake.

Ironically, until this paper, Drake was one of the principle
developers of a
competing and non-turbulent explanation for the rapid release of energy.
In 2000
Drake led a team of scientists that published a widely acclaimed study
indicating that
during the magnetic reconnection process a two-layer flow of particles is
created
that speeds the release of energy. In this laminar flow theory, “whistler
waves”
cause the plasma that is pulled along by the slinging field lines to
divide into two
streams, one of electrons and the other of ionized atoms.

“Based on these latest findings, I think that the correct conceptual

framework for understanding the explosive release of magnetic energy is a
combination of laminar and turbulent mechanisms rather than one or the
other
alone,” Drake said.

“Whistler waves provided a good explanation for every part of this
puzzle except one, and that was the observation that during reconnection
events
like solar flares there is a huge amount of energy going into energetic
electrons.
Our latest findings indicate turbulence may be that missing piece.”

“Formation of Electron Holes and Particle Energization During Magnetic
Reconnection,”
Science, February 7, 2003, J. F. Drake, M. Swisdak and M. A. Shay,
University of Maryland;
C. Cattell, University of Minnesota; B. N. Rogers, Dartmouth College; A.
Zeiler, Max-Planck-Institute, Germany.

SpaceRef staff editor.