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Title: TOWARD A THEORY OF ASTROPHYSICAL PLASMA TURBULENCE AT SUBPROTON SCALES

We present an analytical study of subproton electromagnetic fluctuations in a collisionless plasma with a plasma beta of the order of unity. In the linear limit, a rigorous derivation from the kinetic equation is conducted focusing on the role and physical properties of kinetic-Alfvén and whistler waves. Then, nonlinear fluid-like equations for kinetic-Alfvén waves and whistler modes are derived, with special emphasis on the similarities and differences in the corresponding plasma dynamics. The kinetic-Alfvén modes exist in the lower-frequency region of phase space, ω << k v{sub Ti} , where they are described by the kinetic-Alfvén system. These modes exist both below and above the ion-cyclotron frequency. The whistler modes, which are qualitatively different from the kinetic-Alfvén modes, occupy a different region of phase space, k v{sub Ti} << ω << k{sub z}v{sub Te} , and they are described by the electron magnetohydrodynamics (MHD) system or the reduced electron MHD system if the propagation is oblique. Here, k{sub z} and k are the wavenumbers along and transverse to the background magnetic field, respectively, and v{sub Ti} and v{sub Te} are the ion and electron thermal velocities, respectively. The models of subproton plasma turbulence are discussed and the results of numericalmore » simulations are presented. We also point out possible implications for solar-wind observations.« less
Authors:
; ;  [1] ;  [2]
  1. Department of Physics, University of Wisconsin-Madison, Madison, WI 53706 (United States)
  2. Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States)
Publication Date:
OSTI Identifier:
22270659
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALFVEN WAVES; ASTROPHYSICS; BETA RATIO; COLLISIONLESS PLASMA; COMPUTERIZED SIMULATION; CYCLOTRON FREQUENCY; ELECTRONS; FLUCTUATIONS; KINETIC EQUATIONS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; NONLINEAR PROBLEMS; PHASE SPACE; PLASMA FLUID EQUATIONS; SOLAR WIND; TURBULENCE; WHISTLER INSTABILITY