| 著者名 | Authors | 所属機関名 | 所属機関名(欧文) | |
| 1 | #大村/善治 | Omura/Yoshiharu | 京都大学超高層電波研究センター | Radio Atmospheric Science Center, Kyoto University |
講演予稿:
磁気圏におけるホイッスラーモード波動と相対論的な高エネルギー電子との
相互作用において、相対論的効果が非相対論的扱いによって得られる線形
成長率を抑えるように作用することが、これまでの理論研究によって報告
されている。本研究では、高エネルギー電子の温度異方性によるホイッス
ラーモード不安定性に関して、1次元の電磁粒子シミュレーションを、相対論
コードと非相対論コードの両方を用いて実行する。電子サイクロトロン周波
数とプラズマ周波数の比変化させてパラメータ・ランを実行し、線形理論に
よる成長率の確認と、非線形段階におけるホイッスラー波動の飽和レベルの
評価を行い、非線形波動粒子相互作用によって引き起こされるピッチ角散乱
における相対論的効果の重要性について論じる。
abstract:
Relativistic effects on the linear growth rates of the
whistler mode instability have been studied by a number of
authors including Sentman and Goertz [1978], Sazhin [1993],
Wong and Goldstein [1994], Schlickeiser et al. [1997] and
Xiao et al. [1998]. In these theoretical analyses,
relativistic effects are shown to be quantitatively
important, suppressing the growth rates significantly. To
test the linear theory and to identify the relativistic
effects, we perform a series of one-dimensional
electromagnetic particle simulations using relativistic and
non-relativistic codes. We assume a major background
component of isotropic thermal electrons and a minor
component of anisotropic relativistic electrons in a uniform
magnetic field. Driven by a given temperature anisotropy of
high energy electrons, the whistler mode waves grow to a
nonlinear level at which saturation takes place due to the
nonlinear trapping of resonant electrons and/or quasi-linear
relaxation of the temperature anisotropy. We compare the
saturation level of the instabilities for various cases with
relativistic and nonrelativistic codes and their overall
efficiency in producing pitch angle diffusion. Preliminary
results show that, although the relativistic code gives a
smaller growth rate as predicted by the linear theory, the
waves saturate at a higher amplitude, scattering the
resonant electrons more effectively. Parametric dependence
of the relativistic effects in the nonlinear diffusion
process is studied for several values of the ratio of the
electron cyclotron frequency to the electron plasma frequency.
REFERENCES
Sazhin, S., Whistler-mode Waves in a Hot Plasma, Cambridge
University Press, 1993.
Schlickeiser, R., H. Fichtner, and M. Kneller, J. Geophys.
Res., 102, 4725, 1997.
Sentman, D. D., and C. K. Goertz, J. Geophys. Res., 83, 3151, 1978.
Wong, H. K., and M. L. Goldstein, J. Geophys. Res., 99, 235, 1994.
Xiao, F., R. M. Thorne, and D. Summers, Phys. Plasmas, in press, 1998.
キーワード:
相対論効果, 波動粒子相互作用, プラズマ, 不安定性, 計算機実
Keywords:
whistler, wave-particle interactions, relativistic plasma