Japan Geoscience Union Meeting 2015

Presentation information


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

[P-EM26] Space Plasma Physics: Theory and Simulation

Sun. May 24, 2015 11:00 AM - 12:45 PM 302 (3F)

Convener:*Takayuki Umeda(Solar-Terrestrial Environment Laboratory, Nagoya University), Takanobu Amano(Department of Earth and Planetary Science, University of Tokyo), Yasuhiro Nariyuki(Faculty of Human Development, University of Toyama), Tooru Sugiyama(Japan Agency for Marine-Earth Science and Technology Center for Earth Information Science and Technology), Tadas Nakamura(Fukui Prefectural University), Chair:Tadas Nakamura(Fukui Prefectural University), Masafumi Shoji(Solar-Terrestrial Environment Laboratory, Nagoya University)

11:15 AM - 11:30 AM

[PEM26-09] Dependencies of the generation process of whistler-mode emissions on temperature anisotropy of energetic electrons

*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)

By a series of electron hybrid simulations, we study dependencies of the generation process of whistler-mode chorus and hiss-like emissions on temperature anisotropy of energetic electrons.
Whistler-mode chorus emissions are electromagnetic plasma waves commonly observed in planetary magnetospheres. In the Earth's inner magnetosphere, chorus emissions are observed mostly on the dawn side and are enhanced during geomagnetically disturbed periods. Chorus emissions appear in the typical frequency range from 0.2 to 0.8 fce0 with a gap at the half fce0, where fce0 represents the electron gyrofrequency at the magnetic equator. Recent in situ observation in the magnetosphere revealed the presence of whistler-mode hiss-like emissions, whose wave amplitude is comparable to those of chorus emissions.
The generation process of chorus has been reproduced in electron hybrid simulations and has been explained by the nonlinear wave growth theory [see review by Omura et al., in AGU Monograph "Dynamics of the Earth's Radiation Belts and Inner Magnetosphere, 2012]. The generation mechanism of hiss-like emissions is also explained by the nonlinear wave growth theory and has been reproduced by simulations [Katoh and Omura, JGR 2013]. In the present study, by an improved electron hybrid code with OhHelp library [Nakashima et al., 2009], we conduct a series of electron hybrid simulations for different temperature anisotropy (AT) of the initial velocity distribution function of energetic electrons. We vary AT in the range from 3 to 9 with changing the number density of energetic electrons (Nh) so as to study whether distinct rising-tone chorus emissions are reproduced or not in the assumed initial condition. Based on the simulation results, we reveal properties of the chorus generation for the assumed AT parameter range.