Abstract
Abstract
We determine solar energetic particle (SEP) event He/H peak intensity ratios A
He observed in the four energy channels of the SOHO EPHIN detector covering 4–53 MeV nuc−1. Those SEP A
He values range over two orders of magnitude for 43 large western hemisphere SEP events through the period 1997–2017. A
He of each SEP event are compared with average solar wind (SW) A
He values measured for 8 hr after the SEP event onsets with the solar wind experiment Faraday Cup instrument on Wind. A
He in the 4–8 and 8–21 MeV nuc−1 range are significantly correlated with SW A
He (CC = 0.45 and 0.41), but less so in the 21–41 and 41–53 MeV nuc−1 range, where uncertainties of the A
He values are higher. Median SEP A
He values decline slightly with increasing energy and are ≤0.5 their associated SW values. Both median SEP and SW A
He decline by a factor of ∼2 from the 27 events of cycle 23 to the 16 of cycle 24. Those results suggest a connection between the SW and the seed population of SEP events. An unexpected result is that SEP A
He increases with event peak intensities in our 43 events as He peak intensities increase faster than those of H in larger events.
Funder
DOD ∣ USAF ∣ AFMC ∣ Air Force Office of Scientific Research
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
3 articles.
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