[P-EM17] Space Plasma Science

[PEM17-12] Threshold analysis of lower hybrid and ion Bernstein wave instability driven by energetic ions

*Tsubasa Kotani¹, Mieko Toida², Toseo Moritaka², Satoshi Taguchi¹ (1.Graduate School of Science, Kyoto University, 2.National Institute for Fusion Science)

Keywords:lower hybrid wave, ion Bernstein wave, energetic ions, instability analysis

Taking into account the thermal effects, the lower hybrid wave can be considered as a type of ion Bernstein wave. Assuming that energetic ions, as the driving source of these waves, have a ring-like velocity distribution characterized by the delta function, the instability can be determined by the only four parameters: the ion-to-electron mass m_i/m_e, the ratio of the electron plasma frequency to the electron gyro frequency ω_pe/Ω_e, the ratio of the energetic ion velocity to the bulk ion thermal velocity u_⊥/v_ti, and the density ratio of energetic ions to electrons n_h/n_e. There are many previous studies to investigate a lower hybrid and ion Bernstein wave instability, but most of them used limited parameters to analyze the instability.

In this study, we perform parametric instability analyses for lower hybrid and ion Bernstein waves driven by energetic ions. We consider these waves propagating exactly perpendicular to the magnetic field. We analyze the instability threshold (n_h/n_e) for the two parameters (ω_pe/Ω_e and u_⊥/v_ti ) in a hydrogen-electron (m_i/m_e=1836) plasma.