Some features of the sources of relativistic particles at the Sun in the solar cycles 21-23статья
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Дата последнего поиска статьи во внешних источниках: 28 мая 2015 г.
Аннотация: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 confirmed
by different forms of spectral fitting for PC and DC and by their dynamics as derived from neutron monitor data with optimization
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 function.
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 process
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.