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Non-gyrotropic proton and alpha-particle velocity distributions in the solar wind: TAUS observations and stability analysisIon velocity distribution functions have been measured with high time resolution by the TAUS plasma instrument on the PHOBOS mission to Mars in 1989. The unambiguous separation of protons and alpha-particles by TAUS enabled us to study the nonthermal features of their distributions separately and to analyze the stability of the distributions against excitation of waves in the cyclotron-frequency domain. Typical nonthermal features include temperature anisotropies, with T(sub perpendicular) larger than T(sub parallel), and ion beam populations drifting along the local magnetic field direction. Also, distinctly non-gyrotropic alpha-particle velocity distributions were sometimes found. Non-gyrotropy strongly changes the wave dispersion and gives rise to new growing modes, related to the coupling of the standard wave modes existing in gyrotropic plasma. It is found that for the measured non-gyrotropic ion distributions the right-hand polarized wave can also be excited by a temperature anistropy instead of the usual beam drift.
Document ID
19960021395
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
Authors
Astudillo, H. F.
(Max-Planck-Inst. fuer Aeronomie Katlenburg-Lindau, Germany)
Marsch, E.
(Max-Planck-Inst. fuer Aeronomie Katlenburg-Lindau, Germany)
Livi, S.
(Max-Planck-Inst. fuer Aeronomie Katlenburg-Lindau, Germany)
Rosenbauer, H.
(Max-Planck-Inst. fuer Aeronomie Katlenburg-Lindau, Germany)
Date Acquired
August 17, 2013
Publication Date
June 30, 1995
Publication Information
Publication: International Solar Wind 8 Conference
Subject Category
Solar Physics
Accession Number
96N24791
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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