Solar neutron events associated with large solar flares in solar cycle 23

Details Solar neutron events associated with large solar flares in solar cycle 23 Solar neutron events associated with large solar flares in solar cycle 23

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsh13a0292w&link_type=abstract

American Geophysical Union, Fall Meeting 2005, abstract #SH13A-0292

Astronomy and Astrophysics

Astrophysics

7500 Solar Physics, Astrophysics, And Astronomy, 7514 Energetic Particles (2114), 7519 Flares, 7554 X-Rays, Gamma Rays, And Neutrinos

Scientific paper

We have investigated ion acceleration mechanisms in solar flares by observing solar neutrons produced by in association with these solar flares. Solar neutrons are observed by means of ground-based neutron monitors and solar neutron telescopes which form an international network for solar neutron observations. Observations of solar neutrons have been made during solar cycle 23 using this network. More than a hundred X class flares have been recorded in solar cycle 23. Corresponding to these, five solar neutron events were observed by ground-based neutron monitors from the flares of November 24, 2000, August 25, 2001, October 28, November 2 and 4, 2003. The statistical significances of all these events were, very significant (more than 5 σ), and the excesses were clear. These solar neutron events observed in solar cycle 23 were detected in association with strong emissions of hard X-rays and γ -rays. The occurrence of solar neutrons appears to be correlated with the intensity of hard X-rays and γ -rays emitted by the associated solar flare as observed by the Yohkoh, RHESSI and INTEGRAL satellites. Assuming that solar neutrons are produced at the same time as the emission of these γ -rays, a good correlation is found between the production times of solar neutrons and the observed excesses of neutron monitors. The corresponding energy spectra of solar neutrons at the solar surface is well described by a power law. The spectral indexes of the solar neutron events we have observed in solar cycle 23 are typical for the solar neutron events observed so far, being between -3 and -4, although the fluxes are fainter than those observed in earlier events. From the spectra of solar neutrons, the energy spectra of accelerated ions can be deduced and these are found to be softer than the neutron spectra, which have spectral indexes between -4 and -5. The corresponding number of protons above 30 MeV was estimated to be between 1030 and 1033 for these events.

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