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Mixing the Solar Wind Proton and Electron Scales: Effects of Electron Temperature Anisotropy on the Oblique Proton Firehose InstabilityThe double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons, unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much faster and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma β and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.
Document ID
Document Type
Reprint (Version printed in journal)
Maneva, Y. (Centre for Mathematical Plasma Astrophysics Heverlee, Belgium)
Lazar, M. (Centre for Mathematical Plasma Astrophysics Heverlee, Belgium)
Vinas, A. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Poedts, S. (Centre for Mathematical Plasma Astrophysics Heverlee, Belgium)
Date Acquired
January 31, 2017
Publication Date
November 17, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 832
Issue: 1
Subject Category
Plasma Physics
Report/Patent Number
Distribution Limits
solar wind