Researchers discover source of super-fast electron 'rain'
The downpours, which can affect satellites and space travel, are caused
by electromagnetic whistler waves, scientists say
Date:
March 29, 2022
Source:
University of California - Los Angeles
Summary:
Scientists have discovered a new source of super-fast, energetic
electrons raining down on Earth's atmosphere, a phenomenon that
contributes to the colorful aurora borealis and poses hazards to
satellites, spacecraft and astronauts.
FULL STORY ==========================================================================
UCLA scientists have discovered a new source of super-fast, energetic
electrons raining down on Earth, a phenomenon that contributes to the
colorful aurora borealis but also poses hazards to satellites, spacecraft
and astronauts.
==========================================================================
The researchers observed unexpected, rapid "electron precipitation" from
low- Earth orbit using the ELFIN mission, a pair of tiny satellites built
and operated on the UCLA campus by undergraduate and graduate students
guided by a small team of staff mentors.
By combining the ELFIN data with more distant observations from NASA's
THEMIS spacecraft, the scientists determined that the sudden downpour
was caused by whistler waves, a type of electromagnetic wave that
ripples through plasma in space and affects electrons in the Earth's magnetosphere, causing them to "spill over" into the atmosphere.
Their findings, published March 25 in the journal Nature Communications, demonstrate that whistler waves are responsible for far more electron
rain than current theories and space weather models predict.
"ELFIN is the first satellite to measure these super-fast electrons," said Xiaojia Zhang, lead author and a researcher in UCLA's department of Earth, planetary and space sciences. "The mission is yielding new insights due
to its unique vantage point in the chain of events that produces them."
Central to that chain of events is the near-Earth space environment,
which is filled with charged particles orbiting in giant rings around
the planet, called Van Allen radiation belts. Electrons in these belts
travel in Slinky-like spirals that literally bounce between the Earth's
north and south poles. Under certain conditions, whistler waves are
generated within the radiation belts, energizing and speeding up the
electrons. This effectively stretches out the electrons' travel path so
much that they fall out of the belts and precipitate into the atmosphere, creating the electron rain.
One can imagine the Van Allen belts as a large reservoir filled with
water - - or, in this case, electrons, said Vassilis Angelopolous, a
UCLA professor of space physics and ELFIN's principal investigator. As
the reservoir fills, water periodically spirals down into a relief drain
to keep the basin from overflowing. But when large waves occur in the reservoir, the sloshing water spills over the edge, faster and in greater volume than the relief drainage.
ELFIN, which is downstream of both flows, is able to properly measure
the contributions from each.
The low-altitude electron rain measurements by ELFIN, combined with the
THEMIS observations of whistler waves in space and sophisticated computer modeling, allowed the team to understand in detail the process by which
the waves cause rapid torrents of electrons to flow into the atmosphere.
The findings are particularly important because current theories and
space weather models, while accounting for other sources of electrons
entering the atmosphere, do not predict this extra whistler wave-induced electron flow, which can affect Earth's atmospheric chemistry, pose
risks to spacecraft and damage low-orbiting satellites.
The researchers further showed that this type of radiation-belt electron
loss to the atmosphere can increase significantly during geomagnetic
storms, disturbances caused by enhanced solar activity that can affect near-Earth space and Earth's magnetic environment.
"Although space is commonly thought to be separate from our
upper atmosphere, the two are inextricably linked," Angelopoulos
said. "Understanding how they're linked can benefit satellites and
astronauts passing through the region, which are increasingly important
for commerce, telecommunications and space tourism." Since its inception
in 2013, more than 300 UCLA students have worked on ELFIN (Electron Losses
and Fields investigation), which is funded by NASA and the National
Science Foundation. The two microsatellites, each about the size of a
loaf of bread and weighing roughly 8 pounds, were launched into orbit
in 2018, and since then have been observing the activity of energetic
electrons and helping scientists to better understand the effect of
magnetic storms in near- Earth space. The satellites are operated from
the UCLA Mission Operations Center on campus.
========================================================================== Story Source: Materials provided by
University_of_California_-_Los_Angeles. Note: Content may be edited for
style and length.
========================================================================== Related Multimedia:
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An_artist's_rendering_of_one_of_UCLA's_bread_loaf-sized_ELFIN_satellites
in_low-Earth_orbit.
========================================================================== Journal Reference:
1. Xiao-Jia Zhang, Anton Artemyev, Vassilis Angelopoulos, Ethan
Tsai, Colin
Wilkins, Satoshi Kasahara, Didier Mourenas, Shoichiro Yokota,
Kunihiro Keika, Tomoaki Hori, Yoshizumi Miyoshi, Iku Shinohara,
Ayako Matsuoka.
Superfast precipitation of energetic electrons in the radiation
belts of the Earth. Nature Communications, 2022; 13 (1) DOI:
10.1038/s41467-022- 29291-8 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220329191722.htm
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