THE SOLAR-FLARE EVENT ON 1990 MAY 24 - EVIDENCE FOR 2 SEPARATE PARTICLE ACCELERATIONS

It has been reported that direct solar neutrons were measured by cosmic-ray neutron monitors (NMs) in the first increase of the solar cosmic-ray event on 1990 May 24 (see work by Shea et al.). A careful study of this first increase led us to conclude that there were no solar neutrons detected by the North American NMs. A semiquantitative analysis of the records of a few NM stations with good response to the first and/or the second increase suggests that the first increase beginning during the interval 2045-2050 UT was produced by solar protons presumably accelerated at the Sun in the impulsive phase of the flare; and that the second larger increase which started no earlier than 2105 UT was probably due to solar protons accelerated by an extended coronal shock. We report preliminary results of an analysis of this solar cosmic-ray event which provides evidence for two entirely separate accelerations of protons from two separate particle populations at the Sun. The optical class 1B solar flare was at heliographic coordinates 36-degrees-N, 76-degrees-W in NOAA region 6063.