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Record 1 of 15763
The Variance of Solar Wind Magnetic Fluctuations: Solutions and Further Puzzles
Author and Affiliation:
Roberts, D. A.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Goldstein, M. L.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Abstract: We study the dependence of the variance directions of the magnetic field in the solar wind as a function of scale, radial distance, and Alfvenicity. The study resolves the question of why different studies have arrived at widely differing values for the maximum to minimum power (approximately equal to 3:1 up to approximately equal to 20:1). This is due to the decreasing anisotropy with increasing time interval chosen for the variance, and is a direct result of the "spherical polarization" of the waves which follows from the near constancy of |B|. The reason for the magnitude preserving evolution is still unresolved. Moreover, while the long-known tendency for the minimum variance to lie along the mean field also follows from this view (as shown by Barnes many years ago), there is no theory for why the minimum variance follows the field direction as the Parker angle changes. We show that this turning is quite generally true in Alfvenic regions over a wide range of heliocentric distances. The fact that nonAlfvenic regions, while still showing strong power anisotropies, tend to have a much broader range of angles between the minimum variance and the mean field makes it unlikely that the cause of the variance turning is to be found in a turbulence mechanism. There are no obvious alternative mechanisms, leaving us with another intriguing puzzle.
Publication Date: Dec 11, 2006
Document ID:
20070032074
(Acquired Oct 30, 2007)
Subject Category: SOLAR PHYSICS
Document Type: Conference Paper
Meeting Information: 2006 American Geophysical Union Fall Meeting; 11-15 Dec. 2006; San Francisco, CA; United States
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: SOLAR WIND; VARIANCE; SOLAR MAGNETIC FIELD; MAGNETOHYDRODYNAMIC WAVES; TURBULENCE; ANISOTROPY
Availability Source: Other Sources
Availability Notes: Abstract Only
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