首页|Proton Cyclotron Instability Threshold Condition of Suprathermal Protons by Kappa Distribution
Proton Cyclotron Instability Threshold Condition of Suprathermal Protons by Kappa Distribution
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NETL
NSTL
Observation has clearly shown that natural space plasmas generally possess a pronounced non-Maxwellian high-energy tail distribution that can be well modeled by a kappa distribution. In this study we investigate the proton cyclotron wave instability driven by the temperature anisotropy (T_⊥/T_‖> 1) of suprathermal protons modeled with a typical kappa distribution in the magnetosheath. It is found that as in the case for a regular bi-Maxwellian, the suprathermal proton temperature anisotropy is subject to the threshold condition of this proton cyclotron instability and the instability threshold condition satisfies a general form T_⊥/T_‖ - 1 = S/β_‖~α, with a very narrow range of the fitting parameters: 0.40 approx< a approx< 0.45, and a relatively sensitive variation 0.27 approx< S approx< 0.65, over 0.01 ≤ β_‖ ≤ 10. Furthermore, the difference in threshold conditions between the kappa distribution and the bi-Maxwellian distribution is found to be small for a relatively strong growth but becomes relatively obvious for a weak wave growth. The results may provide a deeper insight into the physics of this instability threshold for the proton cyclotron waves.
NETL
NSTL
