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

In this paper, we are primarily concerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor and the time profiles of hard X-rays and gamma-rays obtained with the GRANAT satellite (Pelaez et al., 1992; Talon et al., 1993; Terekhov et al., 1993). We compare the derived neutron injection function with macroscopic parameters of the flare region as obtained 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, we consider a two-component neutron injection function, Q(E, t), with the 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 time of the fast (slow) injection component, respectively. By comparing the calculated neutron counting rate with the observations from the Climax neutron monitor we derive the best-fit parameters as T-f approximate 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) approximate 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 regarded as the source for the fast-decaying component of gamma-rays (57.5-110 MeV) and for the fast component of neutron emission. From microwave visibility and the microwave total power spectrum we postulate the presence of a rather big loop (approximate to 2 x 10(5) km), which we regard as being responsible for the slow-decaying component of the high-energy emission. We show how the neutron and gamma-ray emission data can be explained in terms of the macroscopic parameters derived from the H alpha and microwave observations. (3) The H alpha observations also reveal the presence of a fast mode MHD shock (the Moreton wave) which precedes the microwave peak by 20-30 s and the peak of gamma-ray intensity by 40-50 s. From this relative timing and the single-pulsed time profiles of both radiations, we can attribute the whole event as due to a prompt acceleration of both electrons and protons by the shock and subsequent deceleration of the trapped particles while they propagate inside the magnetic loops.