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Spectral analysis of magnetohydrodynamic fluctuations near interplanetary schocksEvidence for two types of relatively large amplitude MHD waves upstream and downstream of quasi-parallel forward and reverse interplanetary shocks is presented. The first mode is an Alfven wave with frequencies (in the spacecraft frame) in the range of 0.025 to 0.07 Hz. This is a left-hand polarized mode and propagates within a few degrees of the ambient magnetic field. The second is a fast MHD mode with frequencies in the range of 0.025 to 0.17 Hz, right-hand polarization and propagating along the magnetic field. These waves are detected principally in association with quasi-parallel shock. The Alfven waves are found to have plasma rest frame frequencies in the range of 1.1 to 6.3 mHz with wavelengths in the order of 4.8 x 10 to the 8th power to 2.7 x 10 to the 9th power cm. Similarly, the fast MHD modes have rest frame frequencies in the range 1.6 to 26 mHz with typical wavelengths about 2.19 x 10 to the 8th power cm. The magnetic field power spectrum in the vicinity of these interplanetary shocks is much steeper than f to the -s/3 at high frequencies. The observed spectra have a high frequency dependence of f to the -2/5 to f to the -4.
Document ID
19840004976
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Vinas, A. F. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Goldstein, M. L. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Acuna, M. H. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
September 4, 2013
Publication Date
November 1, 1983
Subject Category
Astrophysics
Report/Patent Number
NASA-TM-85119
NAS 1.15:85119
Accession Number
84N13044
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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