ELFIN CubeSat discovers ultrafast electron rain source

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Electrons in Earth’s radiation belts appear as yellow and red cross-sections, usually spiraling back and forth, bouncing between the poles. However, belt disturbances can knock electrons out of their typical orbits, knocking them to the North and South Poles, where they can trigger auroras. Credit: Emmanuel Masongsong

Using a " data-gt-translate-attributes="[{" attribute="">Nasa-funded by CubeSat, scientists have discovered a new source of ultra-fast, energetic electrons raining down on our planet, which may have implications for space infrastructure and atmospheric modeling.

Scientists at the University of California, Los Angles (UCLA) observed this rain, known as “electron rush”, from low Earth orbit using the ELFIN (Electron Losses and Fields) mission. Investigation). ELFIN is a pair of small cube-shaped satellites known as CubeSats. It was built and operated by UCLA undergraduate and graduate students under the guidance of a small team of mentors.

Combining ELFIN data with more distant observations of NASA’s macroscale temporal history of events and interactions during substorms, or THEMIS, spacecraft, scientists determined that electron rain was caused by hissing waves, a type of electromagnetic wave that propagates through plasma in the space. Their results, published in Nature Communicationfound more electron precipitation than leading theories had previously predicted.

“ELFIN is the first satellite to measure these ultra-fast electrons,” said Xiaojia Zhang, lead author of the new paper and a researcher in UCLA’s Department of Earth, Planetary, and Space Sciences (EPSS). “The mission offers new perspectives because of its unique perspective.”

THEMIS and ELFIN satellites

The THEMIS and ELFIN satellites (orbits shown in cyan and green, respectively) worked together to help unravel the mystery of the electron shower. When whistling waves (purple) interact with electrons, they can give them extra energy (red spiral), causing them to fall into the atmosphere. Credit: Zhang et al. 2022

The near-Earth space environment is highly dynamic and filled with charged particles orbiting in giant rings around the planet called the Van Allen radiation belts. Similar to a coiled slinky bouncing back and forth between two hands, the electrons in the radiation belts travel in spirals between the Earth’s north and south magnetic poles. Under certain conditions, electromagnetic vibrations called whistling waves can occur in radiation belts, energizing and accelerating electrons so much that they can be lost to the atmosphere, creating electron rain.

By combining THEMIS observations of the whistling waves, electronic data from ELFIN and sophisticated computer modelling, the team saw how the whistling waves caused a rapid torrent of electrons into the atmosphere, far beyond the expected amount. previous theories. Current space weather models don’t account for this extra electron flux, which not only contributes to dazzling auroras, but can also damage low-orbiting satellites and affect atmospheric chemistry.

“It’s really a rewarding feeling to have increased our knowledge of space science, using data from the hardware we’ve built ourselves,” said Colin Wilkins, co-author, instrument manager and space physics PhD student. at EPSS. “It takes tremendous effort and determination behind the scenes to make this happen.”

The team further showed that this kind of radiation belt loss in the atmosphere can increase significantly during geomagnetic storms, which are disturbances caused by increased solar activity that can affect near-Earth space. Existing models do not take this into account, thereby underestimating the effects of electron precipitation.

Considering the impact of electron losses on the atmosphere is important not only for Earth modeling, but also for understanding Earth’s magnetic environment and predicting hazards to satellites, astronauts, and spacecraft. other space infrastructure. Although space is commonly thought to be separate from our upper atmosphere, the two are inextricably linked. Understanding how they are linked can benefit the satellites and astronauts passing through the region, which are increasingly important for commerce, Earth surveillance, telecommunications and tourism.

“The ELFIN mission gave UCLA students the chance to work on an industrial-caliber project right on campus, and I’m proud that we were able to accomplish so much with over 300 undergraduates without sacrificing the quality of science,” said Ethan Tsai, co-author, project leader and PhD student in space physics. “The data from ELFIN satellites is at the forefront of space weather studies and will be widely used by researchers around the of the next decade, so we have worked very hard to make our data open and easily accessible to all of space science. community.”

Reference: “Ultrafast Energetic Electron Precipitation in Earth’s Radiation Belts” by 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 and Ayako Matsuoka, March 25, 2022, Nature Communication.
DOI: 10.1038/s41467-022-29291-8

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