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The solar cycle variation of the solar wind helium abundanceA critical survey was made of the experimental evidence for a variation of the relative abundance by number h, (n alpha/np), of helium in the solar wind. The abundance is found to vary by delta h = 0.01 + or - 0.01 from 0.035 to 0.045 over solar cycle 20. Changes in the average bulk speed during the solar activity cycle was insufficient to account for this increase in h with the solar cycle. The slope of the linear relation between h and the plasma bulk speed is also found to vary, being greatest around solar maximum. An attempt is made to explain the 30% variation in h as the result of the variation in the number of major solar flares over a solar cycle. These obvious transients are apparently not numerous enough to explain the observed variation, but the reasonable expectation remains that the transients observed recently by Skylab which may occur more frequently than major flares could augment those associated with major flares. Since the solar wind flux is not observed to increase at solar maximum, the abundance of Helium cannot be proportional to the proton flux leaving the sun unless the solar wind comes from a smaller area of the sun at maximum than at minimum.
Document ID
19740020148
Acquisition Source
Legacy CDMS
Document Type
Preprint (Draft being sent to journal)
Authors
Ogilvie, K. W. (National Center for Atmospheric Res. Greenbelt, MD, United States)
Hirshberg, J. (NASA Goddard Space Flight Center)
Date Acquired
September 3, 2013
Publication Date
June 1, 1974
Subject Category
Space Radiation
Report/Patent Number
X-690-74-187
NASA-TM-X-70685
Accession Number
74N28261
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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