Electron acceleration by Z-mode waves associated with cyclotron maser instability

Abstract

We demonstrate by a particle simulation that Z-mode waves generated by the cyclotron maser instability can lead to a significant acceleration of energetic electrons. In the particle simulation, the initial electron ring distribution leads to the growth of Z-mode waves, which then accelerate and decelerate the energetic ring electrons. The initial ring distribution evolves into an X-like pattern in momentum space, which can be related to the electron diffusion curves. The peak kinetic energy of accelerated electrons can reach 3 to 6 times the initial kinetic energy. We further show that the acceleration process is related to the "nonlinear resonant trapping" in phase space, and the test-particle calculations indicate that the maximum electron energy gain De max is proportional to B 0:57 w , where B w is the wave magnetic field.

Electron acceleration by Z-mode and whistler-mode waves

“…The formation of X-like electron distribution in the case with a ¼ 0:33 roughly coincides with the diffusion curves of the parallel Z-mode waves with high phase velocity and can be explained by one-wave resonant diffusion. 7,13 In the case with a ¼ 5, the initial electron ring distribution evolves into a shell shape, which is essentially the same as the corresponding diffusion curves. However, the acceleration of electrons by the whistler mode with medium phase velocity in the case with a ¼ 1 cannot be explained by the diffusion curves.…”

“…In the two-and four-wave cases, the huge increment of electron energy is due to simultaneous acceleration by counter-propagating waves. 7 During this stage, electrons are accelerated primarily in the perpendicular direction. After that, electron motion is dominated by waves in one direction, while the waves in the opposite direction just give a small modulation in energy and momentum.…”

“…In our previous study, we showed that the electron ring distribution excites, through cyclotron maser process, 5 the X-mode waves mainly in the perpendicular direction, Z-mode waves in the perpendicular and parallel directions, and whistler-mode waves mainly in the parallel direction. 6,7 The parallel Z-mode waves lead to electron acceleration and formation of X-like momentum distribution. 7 The electron ring distributions can be produced in quasi-perpendicular shocks, 8,9 by mirror reflection of energetic plasma beam in coronal flux loops 10 and by injection of electron beam in the direction perpendicular to magnetic field.…”

“…6,7 The parallel Z-mode waves lead to electron acceleration and formation of X-like momentum distribution. 7 The electron ring distributions can be produced in quasi-perpendicular shocks, 8,9 by mirror reflection of energetic plasma beam in coronal flux loops 10 and by injection of electron beam in the direction perpendicular to magnetic field. 11 In this paper, we present the results of particle simulations and test-particle calculations.…”

The fast development of solar terrestrial sciences in Taiwan

“…Liu et al (2016) surveyed the worst-case GPS scintillations on the ground estimated from radio occultation observations of F3/C during 2007-2014 and are ready to develop an empirical model for the ionospheric S4 scintillation. Currently, the nowcast and forecast data assimilation models with the neutral atmosphere have been developed (Lee et al 2012c;Hsu et al 2014;Sun et al 2015).…”