A study of MHD fluctuations upstream and downstream of quasi-parallel interplanetary shocks

Journal Article · Sat Feb 28 23:00:00 EST 1987 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA092iA03p02243· OSTI ID:5557982

Luttrell, A H; Richter, A K ^[1]

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1. Max-Planck-Inst. fur Aeronomie, Katlenburg-Lindau (West Germany)

Applying power, coherence and magnetic and cross helicity spectral analysis of the solar wind plasma and magnetic field data obtained by Helios-1 and -2, the authors investigate the nature of MHD fluctuations occurring upstream and downstream of a parallel, supercritical, turbulent, of a quasi-parallel, supercritical, turbulent, and of a quasi-parallel, subcritical, laminar fast-forward shock wave. The main results of the investigation are as follows: (1) The spectral slopes and powers very significantly with the length of the data interval analyzed. The difference upstream of the parallel shock was such that the ratio of the axisymmetric spatial diffusion coefficients of a 1-MeV proton, calculated from the 86.4-min and 10.8-min spectra using Morfill and Scholer's (1977) formula, is 11.82. (2) Counterstreaming Alfven waves were identified immediately upstream and downstream of the quasi-parallel, supercritical shock. (3) Fast magnetoacoustic waves were identified upstream of the quasi-parallel, subcritical shock and far upstream of the quasi-parallel, supercritical shock coinciding with the inclusion of a small transverse discontinuity in the spectral analysis. (4) Compressional turbulence which is not characteristic of either of the magnetoacoustic modes was observed downstream of the parallel, supercritical and quasi-parallel subcritical shocks. As regards the determination of the parallel diffusion coefficient from power spectra of the observed magnetic field fluctuations, we may conclude from our results that this procedure is susceptible to major errors due to the following reasons: first, there is no complete theory for the diffusion of energetic particles in regions where the MHD fluctuations cannot be labeled Alfvenic or magnetoacoustic. Second, equations for particle motion in a field of counterstreaming Alfven waves (second Fermi process) are also lacking.

• OSTI ID: 5557982
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 92:A3; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ALFVEN WAVES
BARYONS
DATA ANALYSIS
ELEMENTARY PARTICLES
FERMIONS
FLUCTUATIONS
FLUID MECHANICS
HADRONS
HYDRODYNAMICS
HYDROMAGNETIC WAVES
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
MAGNETIC FIELDS
MAGNETOACOUSTIC WAVES
MAGNETOHYDRODYNAMICS
MECHANICS
NUCLEONS
PROTONS
RADIATIONS
REFLECTION
SATELLITES
SHOCK WAVES
SOLAR ACTIVITY
SOLAR PARTICLES
SOLAR PROTONS
SOLAR RADIATION
SOLAR WIND
SPACE
STELLAR RADIATION
TURBULENCE
VARIATIONS