Japan Geoscience Union Meeting 2018

Presentation information

[EE] Evening Poster

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

[P-EM16] Dynamics of Earth's Inner Magnetosphere and Initial Results from Arase

Tue. May 22, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Danny Summers(Memorial University of Newfoundland), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Keisuke Hosokawa(電気通信大学大学院情報理工学研究科, 共同), Yusuke Ebihara(Research Institute for Sustainable Humanosphere, Kyoto University)

[PEM16-P02] Simulation study of the dependence of the whistler-mode chorus generation on properties of energetic electrons in the Earth's inner magnetosphere

*Yuto Katoh1, Yoshiharu Omura2, Yohei Miyake3, Hideyuki Usui3, Hiroshi Nakashima4 (1.Graduate School of Science, Tohoku University, 2.Research Institute for Sustainable Humanosphere, Kyoto University, 3.Graduate School of System Informatics, Kobe University, 4.Academic Center for Computing and Media Studies, Kyoto University)

Keywords:whistler-mode chorus, numerical experiments, inner magnetosphere

By a series of self-consistent electron hybrid code simulations, we study the dependence of the generation process of whistler-mode chorus emissions on the properties of the velocity distribution function of energetic electrons. In particular, in the present study, we focus on the temperature anisotropy and density of energetic electrons in the Earth's inner magnetosphere. We use the same magnetic field gradient in the simulation system and different temperature anisotropy AT for the initial distribution of energetic electrons at the magnetic equator. We conduct 6 sets of simulations for different AT from 4 to 9, changing the initial number density Nh of energetic electrons at the equator in each set of simulations. By analyzing the spectra obtained in the simulation results, we identify chorus elements with rising tones in the results for higher Nh but no distinct chorus in smaller Nh. We compare the simulation results with estimations of the threshold and optimum amplitude proposed by the nonlinear wave growth theory. We find that the chorus generation processes reproduced in the simulation results are consistently explained by the theoretical estimates. We also compare the simulation results with linear growth rates for all simulation runs. We find clear disagreement between the spectral characteristics of reproduced chorus and the predictions by the linear theory. The present study clarifies that the spectra of chorus are essentially different from those predicted by the linear theory and are determined fully by nonlinear processes of wave-particle interactions in the chorus generation region.