Arase satellite uncovers coupling between plasma waves and charged particles in Geospace

The hot ion that generated the waves (red) then spread across the field lines and heat up the cold ion (yellow) by transferring their energy to them. A part of the transferred energy goes into generating waves. The ERG Science Team is credited.

A new study published in Physical Review Letters shows that high-frequency plasma waves can be generated through wave-particle interactions by heating up low-energy ion particles.

The generation of "plasma waves" is a signature of the state of matter characterized by free roaming charged particles interacting via the force of the universe. "Fast magnetosonic waves" (MSWs) are a type of wave in the space. Hot protons result in MSWs.

The "electromagnetic ion cyclotron" (EMIC) wave is considered a "low Frequency wave" in thegeospace. Satellite observations show that the waves of MSWs and EMIC occur together. The mechanism underlying this co-occurrence is not clear.

A team of researchers led by Professor Yoshizumi Miyoshi from Nagoya University, Japan, has partially undone this mechanism. Studies have shown that MSWs can heat up the 'cold' ion when they are combined with the heating of low-energy protons. We wondered if the appearance of EMIC waves is coupled with the MSW-mediated ion heating process, because of the recent observation data by the Arase satellite.

The team applied a wave-particle interaction analysis method to the MSWs and EMIC waves to examine the "cross-energycoupling" between them through ion heating. The results showed that part of the energy that was transferred to the "cold" protons went into the EMIC waves. Considering that hot protons were excited by MSWs, they acted as a mediators for energy transfer between hot protons, cold protons, and EMIC waves.

Prof. Miyoshi explains how these findings are important to our knowledge about the space as well, because they cause significant scattering and loss of "killer electrons" in the Van Allen radiation belts. The new energy transfer route for exciting EMIC waves revealed in our study could contribute to improved space weather forecasting, making for safer operations of satellite in the Van Allen radiation belts.

There is more information on the Cross-Energy Couplings from Magnetosonic Waves to Electromagnetic Ion Cyclotron Waves through Cold Ion Heating inside the Plasmaosphere. There is a DOI: 10.137/physRevLett.

Journal information: Physical Review Letters.

The Arase satellite uncovered thecoupling between the waves and particles in the sky.

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