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Title: On the parameter dependence of the whistler anisotropy instability: THE WHISTLER ANISOTROPY INSTABILITY

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1];  [3]; ORCiD logo [4]; ORCiD logo [1]
  1. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles California USA
  2. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles California USA, University Corporation for Atmospheric Research, Boulder Colorado USA
  3. Department of Physics and Astronomy, University of California, Los Angeles California USA
  4. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles California USA, Center for Space Physics, Boston University, Boston Massachusetts USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1402343
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 122; Journal Issue: 2; Related Information: CHORUS Timestamp: 2017-10-23 17:54:50; Journal ID: ISSN 2169-9380
Publisher:
Wiley Blackwell (John Wiley & Sons)
Country of Publication:
United States
Language:
English

Citation Formats

An, Xin, Yue, Chao, Bortnik, Jacob, Decyk, Viktor, Li, Wen, and Thorne, Richard M. On the parameter dependence of the whistler anisotropy instability: THE WHISTLER ANISOTROPY INSTABILITY. United States: N. p., 2017. Web. doi:10.1002/2017JA023895.
An, Xin, Yue, Chao, Bortnik, Jacob, Decyk, Viktor, Li, Wen, & Thorne, Richard M. On the parameter dependence of the whistler anisotropy instability: THE WHISTLER ANISOTROPY INSTABILITY. United States. doi:10.1002/2017JA023895.
An, Xin, Yue, Chao, Bortnik, Jacob, Decyk, Viktor, Li, Wen, and Thorne, Richard M. Fri . "On the parameter dependence of the whistler anisotropy instability: THE WHISTLER ANISOTROPY INSTABILITY". United States. doi:10.1002/2017JA023895.
@article{osti_1402343,
title = {On the parameter dependence of the whistler anisotropy instability: THE WHISTLER ANISOTROPY INSTABILITY},
author = {An, Xin and Yue, Chao and Bortnik, Jacob and Decyk, Viktor and Li, Wen and Thorne, Richard M.},
abstractNote = {},
doi = {10.1002/2017JA023895},
journal = {Journal of Geophysical Research. Space Physics},
number = 2,
volume = 122,
place = {United States},
year = {Fri Feb 24 00:00:00 EST 2017},
month = {Fri Feb 24 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1002/2017JA023895

Citation Metrics:
Cited by: 6works
Citation information provided by
Web of Science

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  • The whistler anisotropy instability is studied in a magnetized, homogeneous, collisionless plasma model. The electrons (denoted by subscript e) are represented initially with a single bi-Maxwellian velocity distribution with a temperature anisotropy T{sub perpendiculare}/T{sub ||e}>1, where perpendicular and || denote directions perpendicular and parallel to the background magnetic field B{sub o}, respectively. Kinetic linear dispersion theory predicts that, if the ratio of the electron plasma frequency {omega}{sub e} to the electron cyclotron frequency {Omega}{sub e} is greater than unity and {beta}{sub ||e}{>=}0.025, the maximum growth rate of this instability is at parallel propagation, where the fluctuating fields are strictly electromagnetic.more » At smaller values of {beta}{sub ||e}, however, the maximum growth rate shifts to propagation oblique to B{sub o} and the fluctuating electric fields become predominantly electrostatic. Linear theory and two-dimensional particle-in-cell simulations are used to examine the consequences of this transition. Three simulations are carried out, with initial {beta}{sub ||e}=0.10, 0.03, and 0.01. The fluctuating fields of the {beta}{sub ||e}=0.10 run are predominantly electromagnetic, with nonlinear consequences similar to those of simulations already described in the literature. In contrast, the growth of fluctuations at oblique propagation in the low electron {beta} runs leads to a significant {delta}E{sub ||}, which heats the electrons leading to the formation of a substantial suprathermal component in the electron parallel velocity distribution.« less
  • Empirical formulae for the real frequency and growth rate associated with the whistler anisotropy instability are obtained. The electrons are assumed to have an anisotropic distribution function, with Maxwellian parallel distribution. Under such an assumption complex roots of the dispersion relation depend only on two dimensionless parameters, namely, the temperature anisotropy factor A = T{sub perpendiculare}/T{sub ||e} - 1, where T{sub perpendiculare} and T{sub ||e} are the perpendicular and parallel electron temperatures, respectively, and parallel electron beta, {beta}{sub ||} = (8{pi}nT{sub ||e}/B{sup 2}){sup 1/2}, where n and B are the plasma density and magnetic field intensity, respectively. Comparison against exactmore » numerical roots show that analytical formulae describe the whistler instability over a wide range of parallel electron beta and temperature anisotropy factor. The present result may be useful for circumstances in which the use of exact numerical roots becomes impractical, such as in the radiation belt quasi-linear transport coefficient calculation.« less
  • The authors model the interaction of whistler waves with the quasi-perpendicular bow shock observed on Nov 7, 1977. Using a Monte Carlo technique they are able to construct the resulting electron distribution function. This distribution function is asymmetric, and includes a loss cone which the data supports. This distribution function asymmetry is able to drive instabilites which couple to generate additional whister energy. A significant amount of the whistler energy is observed to originate from the region where the loss cone is observed.
  • Detailed properties of the cyclotron maser and whistler instabilities in a relativistic magnetized plasma are investigated for a particular choice of anisotropic distribution function F(p/sub perpendicular//sup 2/,p/sub z/) that permits an exact analytical reduction of the dispersion relation for arbitrary energy anisotropy. The analysis assumes electromagnetic wave propagation parallel to a uniform applied magnetic field B/sub 0/e/sub z/. Moreover, the particular equilibrium distribution function considered in the present analysis assumes that all electrons move on a surface with perpendicular momentum p/sub perpendicular/ = p-circumflex/sub perpendicular/ = const and are uniformly distributed in axial momentum from p/sub z/ = -p-circumflex/sub z/more » = const to p/sub z/ = +p-circumflex/sub z/ = const (so-called ''waterbag'' distribution in p/sub z/). This distribution function incorporates the effects of a finite momentum spread in the parallel direction. The resulting dispersion relation is solved numerically, and detailed properties of the cyclotron maser and whistler instabilities are determined over a wide range of energy anisotropy, normalized density ..omega../sub p//sup 2//..omega../sub c//sup 2/, and electron energy.« less
  • 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 parallelmore » 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« less