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Electromagnetic proton cyclotron anisotropy instability: Wave‐particle scattering rate
Author(s) -
Gary S. Peter,
Yin Lin,
Winske Dan
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl000055
Subject(s) - physics , anisotropy , instability , magnetosheath , scattering , proton , cyclotron , condensed matter physics , computational physics , plasma , atomic physics , optics , nuclear physics , magnetosphere , mechanics , magnetopause
The electromagnetic proton cyclotron instability is driven by a proton temperature anisotropy T ⟂p / T ∥p >1 where the directional subscripts denote directions relative to the background magnetic field. Enhanced field fluctuations from instability growth lead to wave‐particle scattering which reduces the anisotropy; previous research has demonstrated that the anisotropy is constrained by a power‐law function of β ∥p . Here two‐dimensional hybrid simulations in a homogeneous, magnetized, collisionless plasma are used to derive a scaling relation for the maximum scattering rate of proton anisotropy reduction. The result is a function only of the anisotropy and β ∥p and so is appropriate for use in fluid models of anisotropic plasmas such as the magnetosheath.