Direct measurements of two-way wave-particle energy transfer in a collisionless space plasma

Abstract

Particle acceleration by plasma waves and spontaneous wave generation are fundamental energy and momentum exchange processes in collisionless plasmas. Such wave-particle interactions occur ubiquitously in space. We present ultrafast measurements in Earth's magnetosphere by the Magnetospheric Multiscale spacecraft that enabled quantitative evaluation of energy transfer in interactions associated with electromagnetic ion cyclotron waves. The observed ion distributions are not symmetric around the magnetic field direction but are in phase with the plasma wave fields. The wave-ion phase relations demonstrate that a cyclotron resonance transferred energy from hot protons to waves, which in turn nonresonantly accelerated cold He to energies up to ~2 kilo-electron volts. These observations provide direct quantitative evidence for collisionless energy transfer in plasmas between distinct particle populations via wave-particle interactions.

Observations of the Source Region of Whistler Mode Waves in Magnetosheath Mirror Structures

“…The amplitude modulation, which was calculated from x and y components of B w (square root of sum of squares) did not have a clear correlation among four spacecraft (Figure 9b). Because the group velocity, which was estimated from N e (Figure 6k), B 0 (Figure 6a), and the wave frequency (Figure 9c) under the cold plasma approximation, was ~3,000 km s −1 , if a pair of spacecraft detected the same wave, a shift of amplitude modulations should be within ~0.015 s. The wave frequency (Figure 9c), which is the inverse of the single rotation period, was calculated from one R‐mode directed rotation period of B w in the x ‐ y (perpendicular) plane centered at each observation time, if the period of half a rotation before the observation time was within a factor of two of that after the observation (Kitamura et al, 2018). Cases where the minimum of the amplitude of B w in x ‐ y plane became smaller than 0.01 nT or the maximum amplitude in a rotation became >1.5 times larger than the minimum amplitude (large amplitude fluctuation in a wave period) were not plotted in Figure 9c.…”

Resonant Whistler‐Electron Interactions: MMS Observations Versus Test‐Particle Simulation

“…The difficulty to approach these processes stems from the need to measure simultaneously the 7-D VDF (three spatial dimensions, three velocity dimensions, and time) with high temporal and velocity space resolutions to access the kinetic scales and the 4-D structure of the electric and magnetic fields. While the latter could have been achieved at the magnetohydrodynamic (MHD) and ion scales using the cluster data and appropriate data analysis techniques (Narita et al, 2010;Sahraoui et al, 2006Sahraoui et al, , 2010, the former became possible only in The method followed in the present study is similar to the approach of Kitamura et al (2018) and Gershman et al (2017), in that we first identify a neat electromagnetic wave, as intense and monochromatic as possible, study its potential effect on particle velocity distribution functions (VDF), and then compare the expected signatures with the VDF observed outside and inside the region where the wave is observed. This approach enables an unequivocal, three-dimensional comparison of resonant signatures in the VDF between observations and the simulation.…”

Estimation of Growth Rate of Electromagnetic Plasma Wave through Vlasov-Maxwell Mathematical Frame in Ionospheric Plasma

“…Solar wind is the main source of energy and momenta to this open plasma system. Both electromagnetic plasma waves and electrostatic plasma waves are interacting by means of wave-wave interaction and waveparticle-wave interaction process within this near-Earth space region [1,2,3,4,5,6].This region has many linear and nonlinear properties for the energy exchange among waves and particles. Complex radiation emission phenomena are observed at different altitudes by ground based and satellite based observatories.…”