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Title: Electron temperature anisotropy instabilities: Whistler, electrostatic and z mode

Abstract

An electron temperature anisotropy T{sub {perpendicular}e}/T{sub {parallel}e}{gt}1 leads to excitation of three distinct instabilities in collisionless plasmas at frequencies below the electron cyclotron frequency {vert_bar}{Omega}{sub e}{vert_bar} (Here {perpendicular} and {parallel} denote directions relative to the background magnetic field {bold B}{sub o}.). Linear Vlasov theory is used to study these growing modes, with emphasis on the scaling of the temperature anisotropy at instability threshold. If the electron plasma frequency {omega}{sub e} is greater than {vert_bar}{Omega}{sub e}{vert_bar} and electrons are sufficiently hot, the whistler is the unstable mode with smallest anisotropy threshold; this electromagnetic mode has maximum growth rate at propagation parallel to {bold B}{sub o}. At {omega}{sub e}{gt}0.5{vert_bar}{Omega}{sub e}{vert_bar}, an electrostatic electron anisotropy instability can arise propagation oblique to {bold B}{sub o}; this mode may have the smallest threshold for sufficiently cool electrons and {omega}{sub e}{approximately}{vert_bar}{Omega}{sub e}{vert_bar}. And T{sub {perpendicular}e}/T{sub {parallel}e}{gt}1 drives the {ital z} mode unstable at {omega}{sub e}{lt}{vert_bar}{Omega}{sub e}{vert_bar}; this electromagnetic mode also has maximum growth rate at parallel propagation and is the persistent instability at {omega}{sub e}{approx_lt}0.5{vert_bar}{Omega}{sub e}{vert_bar}. The results are discussed in connection with observations from the polar and auroral regions of the terrestrial magnetosphere. {copyright} 1999 American Geophysical Union

Authors:
 [1];  [2]
  1. Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
  2. School of Physics, University of Sydney, New South Wales (Australia)
Publication Date:
OSTI Identifier:
688000
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research
Additional Journal Information:
Journal Volume: 104; Journal Issue: A9; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; PLANETARY ATMOSPHERES; IONOSPHERE; WHISTLERS; INTERPLANETARY SPACE; SOLAR WIND; PLASMA INSTABILITY; PLASMA WAVES; DISTURBANCES; WHISTLER INSTABILITY; ELECTRON-ION COLLISIONS

Citation Formats

Gary, S.P., and Cairns, I.H. Electron temperature anisotropy instabilities: Whistler, electrostatic and z mode. United States: N. p., 1999. Web. doi:10.1029/1999JA900296.
Gary, S.P., & Cairns, I.H. Electron temperature anisotropy instabilities: Whistler, electrostatic and z mode. United States. doi:10.1029/1999JA900296.
Gary, S.P., and Cairns, I.H. Wed . "Electron temperature anisotropy instabilities: Whistler, electrostatic and z mode". United States. doi:10.1029/1999JA900296.
@article{osti_688000,
title = {Electron temperature anisotropy instabilities: Whistler, electrostatic and z mode},
author = {Gary, S.P. and Cairns, I.H.},
abstractNote = {An electron temperature anisotropy T{sub {perpendicular}e}/T{sub {parallel}e}{gt}1 leads to excitation of three distinct instabilities in collisionless plasmas at frequencies below the electron cyclotron frequency {vert_bar}{Omega}{sub e}{vert_bar} (Here {perpendicular} and {parallel} denote directions relative to the background magnetic field {bold B}{sub o}.). Linear Vlasov theory is used to study these growing modes, with emphasis on the scaling of the temperature anisotropy at instability threshold. If the electron plasma frequency {omega}{sub e} is greater than {vert_bar}{Omega}{sub e}{vert_bar} and electrons are sufficiently hot, the whistler is the unstable mode with smallest anisotropy threshold; this electromagnetic mode has maximum growth rate at propagation parallel to {bold B}{sub o}. At {omega}{sub e}{gt}0.5{vert_bar}{Omega}{sub e}{vert_bar}, an electrostatic electron anisotropy instability can arise propagation oblique to {bold B}{sub o}; this mode may have the smallest threshold for sufficiently cool electrons and {omega}{sub e}{approximately}{vert_bar}{Omega}{sub e}{vert_bar}. And T{sub {perpendicular}e}/T{sub {parallel}e}{gt}1 drives the {ital z} mode unstable at {omega}{sub e}{lt}{vert_bar}{Omega}{sub e}{vert_bar}; this electromagnetic mode also has maximum growth rate at parallel propagation and is the persistent instability at {omega}{sub e}{approx_lt}0.5{vert_bar}{Omega}{sub e}{vert_bar}. The results are discussed in connection with observations from the polar and auroral regions of the terrestrial magnetosphere. {copyright} 1999 American Geophysical Union},
doi = {10.1029/1999JA900296},
journal = {Journal of Geophysical Research},
number = A9,
volume = 104,
place = {United States},
year = {1999},
month = {9}
}