Solar wind iron abundance variations at speeds greater than 600 km/s, 1972-1976

Details Solar wind iron abundance variations at speeds greater than 600 km/s, 1972-1976 Solar wind iron abundance variations at speeds greater than 600 km/s, 1972-1976

Nov 1983

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983jgr....88.9059m&link_type=abstract

Journal of Geophysical Research (ISSN 0148-0227), vol. 88, Nov. 1, 1983, p. 9059-9068.

Physics

15

Abundance, Iron, Satellite Observation, Solar Wind Velocity, Coronal Holes, Data Correlation, Explorer 47 Satellite, Hydrogen Atoms, Mass Ratios, Solar Cycles

Scientific paper

An analysis has been conducted of the Fe/H ratios in the peaks of high-speed streams during the decline of solar cycle 20 and the following minimum (October 1972-December 1976). The response of the 50- to 200-keV ion channel of The Johns Hopkins University Applied Physics Laboratory energetic particle experiments (EPE) on IMP 7 and 8, which is (in the absence of energetic ions) dominated by solar wind iron ions at high solar wind speeds (V approximately equal to or greater than 600 km/s) as inferred from calibrations of flight spare detectors. The conducted Fe measurements have been compared with solar wind H and He parameters from the Los Alamos National Laboratory instruments on the same spacecraft. In general, the Fe distribution parameters (bulk velocity, flow direction, temperature) are found to be similar to the He parameters. Although the average Fe/H ratios found in the peaks of many steady high-speed streams agree within observational uncertainties with the nominal coronal ratio of 4.7 x 10 to the -5th, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated high-speed stream. There are, as well, a factor of 2 variations between stream-averaged abundances for recurrent high-speed streams emanating from different coronal holes occurring on the sun on the same solar rotation. Flare-related solar wind flows sometimes show Fe/H ratios enhanced by factors of 4-5 more than in coronal-hole associated, quiet-time streams, while in one case the Fe/H enhancement was still observable one rotation after the flare activity. Over the period 1973-1976, a steady decrease in the average quiet time Fe/H ratio by a factor of approximately 4 is measured on both IMP 7 and 8.

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