Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

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

[P-EM13] Inner magnetosphere: Recent understanding and new insights

Wed. May 29, 2019 9:00 AM - 10:30 AM A04 (TOKYO BAY MAKUHARI HALL)

convener:Yusuke Ebihara(Research Institute for Sustainable Humanosphere, Kyoto University), Danny Summers(Memorial University of Newfoundland), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Shinji Saito(Graduate School of Science, Nagoya University), Chairperson:Shinji Saito(ISEE, Nagoya University), Yusuke Ebihara(RISH, Kyoto University)

10:15 AM - 10:30 AM

[PEM13-16] Influence of kappa distributions on the sweep rate of whistler mode chorus waves

*Danny Summers1 (1.Memorial University of Newfoundland)

Keywords:kappa distributions, whistler mode waves, chorus sweep rates

Kappa particle distributions typically possess a high-energy power-law tail characterized by a spectral index kappa. Here we consider the bi-kappa and kappa-loss-cone distributions. The influence of kappa distributions on the linear growth rate of whistler-mode waves is mediated by the electron anisotropy. The linear growth rate corresponding to kappa distributions (for kappa=2) exceeds that for a bi-Maxwellian distribution for electron anisotropies less than a critical value; for anisotropies greater than the critical value the opposite applies. The influence of kappa distributions on the threshold wave amplitude for nonlinear growth depends on the wave frequency, the electron anisotropy and the temperature of the (hot) energetic electrons that generate the waves. We construct time profiles of the amplitude and frequency of chorus wave elements for various sets of parameters. We examine how the sweep (chirp) rate of the waves depends on the kappa index. Nonlinear growth of whistler mode waves can be enhanced or inhibited by kappa distributions,dependent on the values of the parameters of the background plasma and the properties of the injected energetic electron population that generates the waves.