Some features of the sources of relativistic particles at the Sun in the solar cycles 21–23 E.V. Vashenyuk a, * , Yu.V. Balabin a , J. Perez-Peraza b , A. Gallegos-Cruz c , L.I. Miroshnichenko d a Polar Geophysical Institute, PGI, Cosmic Ray Group, 14, Fersman Street, Apatity, Murmansk Region 184209, Russia b Instituto de Geofisica, UNAM, C.U., Coyoacan, 04510 Mexico D.F., Mexico c UPIICSA, IPN, Iztacalco, 08400 Mexico D.F., Mexico d IZMIRAN, Troitsk, Moscow Region 142190, Russia Received 1 November 2004; received in revised form 6 May 2005; accepted 6 May 2005 Abstract Regularities of relativistic solar protons (RSP) generation and release from the Sun in the events of 21–23 solar cycles on data of neutron monitors, balloons and spacecraft have been studied. In all, 11 Ground Level Enhancements (GLE) of solar cosmic rays (SCR) were analyzed. The two-peak structure of solar proton intensity profiles gives certain evidence of that two distinct particle populations (components) exist: the early impulse-like intensity increase with a hard energy spectrum (prompt component, PC) and late gradual increase with a soft energy spectrum (delayed component, DC). The existence of two RSP populations is also con- firmed by different forms of spectral fitting for PC and DC and by their dynamics as derived from neutron monitor data with opti- mization methods. It is shown that the PC energy spectrum has exponential form that may be an evidence of the acceleration by electric fields arising in the reconnecting current sheets in the corona. The DC energy spectrum may be fitted by a power-law func- tion. Considering the timing of generation and release of two RSP components from the solar corona, the following scenario may be suggested. The prompt component of RSP is produced during initial energy release in a low-coronal magnetic null point. This pro- cess is linked with the H-alpha eruption, onset of CME and type II radio emission. The accelerated particles of PC leave the corona along open field lines with diverging geometry that results in strong focusing of a bunch. Particles of DC originally are trapped in magnetic arches in the low corona and accelerated by a stochastic mechanism at the MHD turbulence in expanding flare plasma. Accelerated particles of DC can be then carried out to the outer corona by an expanding CME. They are released into interplanetary space after the magnetic trap is destroyed giving rise to the source of accelerated particles that is extended in time and azimuth. Ó 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Relativistic solar protons; Acceleration; Energetic spectrum; GLE; Modeling 1. Introduction In this paper, based on the data of neutron monitors, balloons and spacecraft, we consider regularities of rel- ativistic solar protons (RSP) generation and release from the Sun in the events of solar cycles 21–23. In all, eleven Ground Level Enhancements (GLE) of solar cosmic rays (SCR) were analyzed on the data of ground based neutron monitors (NM). The worldwide NM net- work may be considered as a united multidirectional so- lar proton spectrometer in the relativistic energy domain. With the modeling of the NM responses to an anisotropic solar proton flux and comparing them with observations the parameters of primary solar protons outside the magnetosphere can be obtained (e.g., Shea and Smart, 1982; Cramp et al., 1997a,b; Vashenyuk et al., 2003a). This kind of analysis requires 0273-1177/$30 Ó 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2005.05.012 * Corresponding author. Tel.: +7 81555 79173. E-mail address: vashenyuk@pgi.kolasc.net.ru (E.V. Vashenyuk). www.elsevier.com/locate/asr Advances in Space Research 38 (2006) 411–417