JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Poster

P (Space and Planetary Sciences) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM16] [EE] Physics of Inner Magnetosphere Coupling

Wed. May 24, 2017 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL7)

[PEM16-P31] Two-dimensional Particle Simulations of Oblique Whistler-mode Instability

*Takeshi Nogi1, Yoshiharu Omura1 (1.Reserch Institute for Sustainable Humanosphere, Kyoto University)

We perform two-dimensional electromagnetic particle simulations to study basic characteristics of whistler-mode
wave particle interaction involved in chorus emissions propagating oblique to the static magnetic field. We assume
a simple periodic (x, y) system with the magnetic field taken in the x-direction. Assuming energetic electrons
with an anisotropic bi-Maxwellian velocity distribution function, we first test the linear whistler-mode instability
driven by temperature anisotropy to confirm the numerical property of the simulation code. With the electrostatic
components parallel to the magnetic field, which have been neglected in the previous simulation studies on chorus
emissions, we find the linear phase of the instability is much affected by the Electrostatic thermal fluctuations.
It is necessary to put many super-particles in a grid cell to suppress the thermal fluctuation. With 30,000 particles
per cell, we have confirmed a good agreement of the wave growth in the parallel direction with the linear growth
rate. We next put an array of antennas with obliquely aligned to uniform magnetic field, and oscillate the antenna
current with a variable frequency below the electron cyclotron frequency to excite a large amplitude whistler-mode
wave obliquely propagating to the static magnetic field. In addition to the nonlinear trapping of energetic electrons
through the cyclotron resonance, another nonlinear trapping of electrons by the Landau resonance takes place.
Structures of the nonlinear trapping potentials changes with a varying frequency, affecting the efficiency of
energy transfer between the wave and energetic electrons. We study nonlinear evolution of the wave packet, and
competing processes of both resonances in accelerating the energetic electrons to higher energies.