Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability

Abstract

In collision-poor plasmas from space, e.g., the solar wind and planetary magnetospheres, the kinetic anisotropy of the plasma particles is expected to be regulated by the kinetic instabilities. Driven by an excess of ion (proton) temperature perpendicular to the magnetic field $(T_{\perp }>T_{\parallel })$, the electromagnetic ion-cyclotron (EMIC) instability is fast enough to constrain the proton anisotropy, but the observations do not conform to the instability thresholds predicted by the standard theory for bi-Maxwellian models of the plasma particles. This paper presents an extended investigation of the EMIC instability in the presence of suprathermal electrons which are ubiquitous in these environments. The analysis is based on the kinetic (Vlasov-Maxwell) theory assuming that both species, protons and electrons, may be anisotropic, and the EMIC unstable solutions are derived numerically providing an accurate description for conditions typically encountered in space plasmas. The effects of suprathermal populations are triggered by the electron anisotropy and the temperature contrast between electrons and protons. For certain conditions the anisotropy thresholds exceed the limits of the proton anisotropy measured in the solar wind considerably restraining the unstable regimes of the EMIC modes.

Accepted for publication in Astrophysics and space science

References in corpus (1)

• On the interpretation and applicability of $\kappa$-distributions

Cited by in corpus (7)

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• Shaping the solar wind temperature anisotropy by the interplay of electron and proton instabilities
• Whistler instability stimulated by the suprathermal electrons present in space plasmas
• Weibel instability beyond bi-Maxwellian anisotropy
• Electromagnetic Ion-Ion Instabilities in Space Plasmas: Effects of Suprathermal Populations
• Whistler instabilities from the interplay of electron anisotropies in space plasmas: A quasilinear approach
• Electromagnetic ion cyclotron instability stimulated by the suprathermal ions in space plasmas: A quasi-linear approach