Shaping the solar wind temperature anisotropy by the interplay of electron and proton instabilities

Abstract

A variety of nonthermal characteristics like kinetic, e.g., temperature, anisotropies and suprathermal populations (enhancing the high energy tails of the velocity distributions) are revealed by the in-situ observations in the solar wind indicating quasistationary states of plasma particles out of thermal equilibrium. Large deviations from isotropy generate kinetic instabilities and growing fluctuating fields which should be more efficient than collisions in limiting the anisotropy (below the instability threshold) and explain the anisotropy limits reported by the observations. The present paper aims to decode the principal instabilities driven by the temperature anisotropy of electrons and protons in the solar wind, and contrast the instability thresholds with the bounds observed at 1~AU for the temperature anisotropy. The instabilities are characterized using linear kinetic theory to identify the appropriate (fastest) instability in the relaxation of temperature anisotropies $A_{e,p}=T_{e,p,\perp }/T_{e,p,\parallel }\ne 1$. The analysis focuses on the electromagnetic instabilities driven by the anisotropic protons ($A_p\lessgtr 1$) and invokes for the first time a dynamical model to capture the interplay with the anisotropic electrons by correlating the effects of these two species of plasma particles, dominant in the solar wind.

arXiv commentAccepted for publication in Astrophysics and Space Science

References in corpus (3)

• Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
• Cumulative effect of Weibel-type instabilities in counterstreaming plasmas with non-Maxwellian anisotropies
• Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability

Cited by in corpus (12)

• Firehose instabilities triggered by the solar wind suprathermal electrons
• Whistler instability stimulated by the suprathermal electrons present in space plasmas
• The Interplay of the Solar Wind Core and Suprathermal Electrons: A Quasilinear Approach for Firehose Instability
• Weibel instability beyond bi-Maxwellian anisotropy
• Electromagnetic ion cyclotron instability stimulated by the suprathermal ions in space plasmas: A quasi-linear approach
• Electromagnetic Ion-Ion Instabilities in Space Plasmas: Effects of Suprathermal Populations
• A new low-beta regime for unstable proton firehose modes in bi-Kappa distributed plasmas
• Mixing the solar wind proton and electron scales. Theory and 2D-PIC simulations of firehose instability
• Particle-In-Cell simulations of the parallel proton firehose instability influenced by the electron temperature anisotropy in solar wind conditions
• On the interplay of solar wind proton and electron instabilities: Linear and quasi-linear approaches
• Kappa-Maxwellian electrons and Bi-Maxwellian protons in a two-fluid model for fast solar wind
• Numerical simulations of temperature anisotropy instabilities stimulated by suprathermal protons