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Magnetic Alfvén‐cyclotron fluctuations of anisotropic nonthermal plasmas
Author(s) -
Navarro Roberto E.,
Muñoz Víctor,
Araneda Jaime,
Viñas Adolfo F.,
Moya Pablo S.,
Valdivia Juan A.
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020550
Subject(s) - physics , solar wind , plasma , instability , proton , cyclotron , anisotropy , electron , magnetic field , atomic physics , computational physics , nuclear physics , mechanics , quantum mechanics
Abstract Remote and in situ observations in the solar wind show that ion and electron velocity distributions persistently present deviations from thermal equilibrium. Ion anisotropies seem to be constrained by instability thresholds which are in agreement with linear kinetic theory. For plasma states below these instability thresholds, the quasi‐stable solar wind plasma sustains a small but detectable level of magnetic fluctuation power. These fluctuations may be related to spontaneous electromagnetic fluctuations arising from the discreteness and thermal motion of charged particles. Here we study magnetic Alfvén‐cyclotron fluctuations propagating along a background magnetic field in a plasma composed of thermal and suprathermal protons and electrons via the fluctuation‐dissipation theorem. The total fluctuating magnetic power is estimated in a proton temperature anisotropy‐beta diagram for three different families of proton distribution functions, which can be compared to a number of recent measurements in the solar wind.