Angle between the average interplanetary magnetic field and the propagation direction of plane large amplitude Alfven waves

Journal Article · Sat Sep 01 04:00:00 EDT 1979 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL006i009p00713· OSTI ID:5773475

Lichtenstein, B R; Sonett, C P

The direction of the time averaged magnetic field in a large amplitude Alfven wave in the solar wind can be significantly different than the direction of the ambient interplanetary magnetic field B/sub A/, which is not directly observable. The theoretical properties of plane large amplitude Alfven waves in the MHD approximation constrain the time averaged magnetic field to cluster around the direction of minimum variance m, which is aligned with the wave normal n. Thus, spacecraft magnetometer observations in the solar wind of minimum variance directions strongly peaked about the average magnetic field direction, particularly in the leading edges of fast streams, are entirely consistent with plane large amplitude Alfven waves which have wave normals aligned with the directions of minimum variance. These observations also do not necessarily imply that geometrical hydromagnetic calculations for Alfven wave propagation direction in the solar wind are incorrect. However, there is a discrepancy between geometrical hydromagnetics theory and observations that IMF minimum variance directions tend to be aligned with the ideal Parker spiral instead of the radial direction.

• Research Organization: Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721
• OSTI ID: 5773475
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 6:9; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALFVEN WAVES
FLUCTUATIONS
FLUID MECHANICS
HYDRODYNAMICS
HYDROMAGNETIC WAVES
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
RADIATION STREAMING
SOLAR ACTIVITY
SOLAR WIND
VARIATIONS
WAVE PROPAGATION