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Дата изменения: Tue May 5 15:36:02 2009 Дата индексирования: Sun Apr 10 01:20:10 2016 Кодировка: Windows-1251 Поисковые слова: molecular cloud |
ON THE
CORRELATION BETWEEN SPECTRA OF SOLAR MICROWAVE BURSTS
AND
SPECTRA OF PROTON FLUXES NEAR EARTH
I. M. Chertok, V. V.
Grechnev and N. S. Meshalkina
Studies
of an extreme solar event of 20 January 2005 strengthened the contest over of a
long-standing question whether solar energetic particles (SEPs)
arriving at Earth were accelerated in flares or in shocks ahead of coronal mass
ejections (CMEs). Herewith, a question is important about a probable relation
between the energy spectrum of SEP and parameters characterizing the frequency
spectrum of flare microwave bursts. Several papers, which considered previous
solar cycles, showed such a relation to exist, in particular, for protons of
tens of MeV energy. Our paper presents results of
analysis of this relation using data covering the period of 1987-2008. We have
found a significant correlation between an index δ, which is
equivalent to the power-law index of the integral energy spectrum of protons
registered near the Earth orbit in a range of 10-100 MeV,
on the one hand, and parameters of microwave bursts such as a ratio of peak
fluxes at two frequencies (e.g., 9 and 15 GHz) and a microwave peak frequency fm as well. Flares
with hard frequency spectra (S9/S15£1, fm ³ 15 GHz) correspond
to proton fluxes with hard (flat) energy spectra (δ£1.5). Accordingly,
flares with soft radio spectra (S9/S15³1.5, fm £ 5 GHz) correspond
to proton fluxes with soft (steep) energy spectra (δ ³ 1.5-2). We have also
shown that powerful high-frequency bursts with hardest radio spectra (fm ' 30 GHz) can point
at acceleration of significant proton fluxes in flares occurring in strong magnetic
fields. These results provide an important argument in favor of acceleration of
solar energetic particles (at least, during the initial pulse of a SEP event)
mainly in impulsive and post-eruptive energy release in flares rather than in
CME-driven shocks.