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Alfven waves, alpha particles, and pickup ions in the solar windPast studies of the properties of Alfven waves in the solar wind have indicated that (1) the amplitude of the velocity fluctuations is almost always smaller than expected on the basis of the amplitude of the field fluctuations, even when the anisotropy of the plasma is taken into account, and (2) the alpha particles do not participate in the wave motions because they 'surf' on the waves carried by the proton fluid. Ulysses data are used to demonstrate that (1) the discrepancy between the velocity and field fluctuations is greater at high heliographic latitudes than in the ecliptic plane, and (2) the alphas do participate in the waves, being either in phase or out of phase with the proton motions depending on whether the differential flow speed between the alphas and protons is greater than or less than the 'observed' wave speed, B(sub o)(delta v squared / delta B squared)exp 1/2, as determined from the ratio of the amplitudes of the velocity and magnetic fluctuations. It is proposed that the modification of Alfven wave propagation speed is due to pressure anisotropies resulting from asymmetric distributions of interstellar pickup ions. If the proposed explanation is correct, it indicates that scattering of pickup ions onto a (bi)spherical shell may not be as complete as generally supposed.
Document ID
19960021406
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
Authors
Goldstein, B. E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Neugebauer, M.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Smith, E. J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Date Acquired
August 17, 2013
Publication Date
June 30, 1995
Subject Category
Solar Physics
Accession Number
96N24802
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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