Synopsis: Electron Bounce

Experiments show that magnetic waves in a plasma may be effective at controlling energetic electrons.
Synopsis figure
NASA/Tom Bridgman

Solar winds and cosmic rays continually feed charged particles into the radiation belts trapped by Earth’s magnetic field. These high-speed particles pose a hazard to space missions and orbiting satellites, so scientists are considering various schemes to drain or divert them. Now, experiments published in Physical Review Letters show that a type of magnetic wave that propagates in a plasma is unexpectedly effective at scattering trapped, energetic electrons.

Yuhou Wang at the University of California, Los Angeles, and her colleagues discovered the strong wave-particle interaction using the Large Plasma Device, a 20-meter-long cylindrical plasma chamber, housed on the UCLA campus. With microwaves, the researchers heat a fraction of the plasma electrons, which are then trapped in a magnetic potential well, mimicking that of the Earth. In this setup, the electrons, which have energies of up to 3 mega-electron-volts, are detected by x rays that they produce upon colliding with the chamber walls.

The magnetic field lines and surrounding plasma in the chamber are analogous to a massive string that can be “plucked” to produce waves by introducing an oscillating magnetic field. Wang et al. find that when they create such waves, called Alfvén waves, with a small radio-frequency antenna, they see a sizable burst of x rays, suggesting that the waves have strongly scattered the electrons.

For now, Wang et al.’s experiments provide a controlled environment in which to study wave-particle interactions in a plasma that could prove useful for diverting electrons in Earth’s radiation belts. – Jessica Thomas


Announcements

More Announcements »

Subject Areas

AstrophysicsPlasma Physics

Previous Synopsis

Nonlinear Dynamics

Lévy Flight of the Bumblebee

Read More »

Next Synopsis

Atomic and Molecular Physics

Molecular Speed Bump

Read More »

Related Articles

Synopsis: Solar Cycle Affects Cosmic Ray Positrons
Astrophysics

Synopsis: Solar Cycle Affects Cosmic Ray Positrons

Discrepancies in the positron content of cosmic rays measured at different times are explained by the periodic reversal of the solar magnetic field’s direction. Read More »

Focus: LIGO Bags Another Black Hole Merger
Astrophysics

Focus: LIGO Bags Another Black Hole Merger

LIGO has detected a second burst of gravitational waves from merging black holes, suggesting that such detections will soon become routine and part of a new kind of astronomy. Read More »

Viewpoint: Paving the Way to Space-Based Gravitational-Wave Detectors
Cosmology

Viewpoint: Paving the Way to Space-Based Gravitational-Wave Detectors

The first results from the LISA Pathfinder mission demonstrate that two test masses can be put in free fall with a relative acceleration sufficiently free of noise to meet the requirements needed for space-based gravitational-wave detection. Read More »

More Articles