%0 Journal Article
%T On the Onset Time of Several SPE/GLE Events: Indications from High-Energy Gamma-Ray and Neutron Measurements by CORONAS-F
%A Viktoria Kurt
%A Karel Kudela
%A Boris Yushkov
%A Vladimir Galkin
%J Advances in Astronomy
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/690921
%X We analyzed the high-energy gamma and neutron emissions observed by the SONG instrument onboard the CORONAS-F satellite during August 25, 2001, October 28, 2003, November 4, 2003, and January 20, 2005 solar flares. These flares produced neutrons and/or protons recorded near Earth. The SONG response was consistent with detection of the pion-decay gamma emission and neutrons in these events. We supposed that a time profile of the soft X-ray derivative was a good proxy of time behavior of the flare energy release. Then we showed that time intervals of the maximum both of energy release and pion-decay-emission coincided well. We determined the onset time of GLEs 65, 69 on the basis of neutron monitor data using the superposed epoch method. The time of high-energy proton onset on November 4, 2003 was found from the GOES data. The time delay between the high-energy gamma ray observation and the high-energy protons onset time was <5 minutes. This time lag corresponds to the least possible proton propagation time. So, we conclude that in these events both protons interacted in the solar atmosphere and the first protons which arrived to Earth, belonged to one and the same population of the accelerated particles. 1. Introduction Solar energetic protons, as Solar Proton Events (SPE) or Ground Level Enhancement (GLE), are observed directly over long time, most probably since the events on February 28 and March 7 in 1942 were identified by Forbush [1] and named later as GLE 1 and 2, respectively. Altogether during the systematic investigation of the GLEs 71 events were recorded. Lower energy of particles, detected by high-latitude neutrons monitors (NM), is ~450£¿MeV (this threshold is determined by atmospheric absorption), but the effective energy exceeds 1£¿GeV. The minimum energy for medium and low-latitude NM is even higher; it is determined by the geomagnetic cutoff. Satellite measurements allowed us to study accelerated particles below the atmospheric threshold (~400£¿MeV). A list of SPE events (N(>10£¿MeV) > 10£¿protons£¿cm£¿2£¿s£¿1£¿sr£¿1) beginning from 1976 can be found, for example, at [2], http://umbra.nascom.nasa.gov/SEP/, and of GLE events at http://neutronm.bartol.udel.edu/~pyle/GLE_List.txt. GLE connection with solar flares is not in doubt, but still debated question is whether the protons are accelerated up to subrelativistic energies directly during flare energy release or acceleration occurs later when the shock waves propagate in the upper corona. Direct study of the GLE dynamics does not answer this question, because particles¡¯ propagation in the
%U http://www.hindawi.com/journals/aa/2013/690921/