NEUTRON AND ELECTROMAGNETIC EMISSIONS DURING THE 1990 MAY 24 SOLAR-FLARE

In this paper, we are primarily concerned with the solar neutron emiss ion during the 1990 May 24 flare, utilizing the counting rate of the C limax neutron monitor and the time profiles of hard X-rays and gamma-r ays obtained with the GRANAT satellite (Pelaez et al., 1992; Talon et al., 1993; Terekhov et al., 1993). We compare the derived neutron inje ction function with macroscopic parameters of the flare region as obta ined from the Ha and microwave observations made at the Big Bear Solar Observatory and the Owens Valley Radio Observatory, respectively. Our results are summarized as follows: (1) to explain the neutron monitor counting rate and 57.5-110 MeV and 2.2 MeV gamma-ray time profiles, w e consider a two-component neutron injection function, Q(E, t), with t he form Q(E, t) = N-f exp[-E/E(f) - t/T-f] + N-s exp[-E/E(s) - t/T-s], where N-f(s), E(f(s)), and T-f(s) denote number, energy, and decay ti me of the fast (slow) injection component, respectively. By comparing the calculated neutron counting rate with the observations from the Cl imax neutron monitor we derive the best-fit parameters as T-f approxim ate to 20 s, E(f) approximate to 310 MeV, T-s approximate to 260 s, E( s) approximate to 80 MeV, and N-f(E > 100 MeV)/N-s (E > 100 MeV) appro ximate to 0.2. (2) From the H alpha observations, we find a relatively small loop of length approximate to 2 x 10(4) km, which may be regard ed as the source for the fast-decaying component of gamma-rays (57.5-1 10 MeV) and for the fast component of neutron emission. From microwave visibility and the microwave total power spectrum we postulate the pr esence of a rather big loop (approximate to 2 x 10(5) km), which we re gard as being responsible for the slow-decaying component of the high- energy emission. We show how the neutron and gamma-ray emission data c an be explained in terms of the macroscopic parameters derived from th e H alpha and microwave observations. (3) The H alpha observations als o reveal the presence of a fast mode MHD shock (the Moreton wave) whic h precedes the microwave peak by 20-30 s and the peak of gamma-ray int ensity by 40-50 s. From this relative timing and the single-pulsed tim e profiles of both radiations, we can attribute the whole event as due to a prompt acceleration of both electrons and protons by the shock a nd subsequent deceleration of the trapped particles while they propaga te inside the magnetic loops.