Deduced spectrum of interacting protons accelerated after the impulsive phase of the 15 June 1991 solar flare
L. Kocharov 1,
H. Debrunner 2,
J. Lockwood 3,
M. McConnell 3,
P. Nieminen 2,
G. Rank 4,
J. Ryan 3 and
V. Schönfelder 4
Received 11 March 1998 / Accepted 15 September 1998
In June 1991 the Sun produced a famous series of six powerful flares. For the solar eruption on 15 June 1991 there exists a rich set of measurements, including in particular -ray and neutron observations of the COMPTEL instrument on board the COMPTON Gamma Ray Observatory (CGRO) satellite. The -ray and neutron emissions indicate prolonged acceleration of protons well after the impulsive phase of the flare. Some accelerated particles interact with solar matter and produce -rays and neutrons at the Sun, others escape into the interplanetary medium. Here we present the deduced energy spectrum of the interacting protons for a nearly one hour period in the gradual phase of the flare. From the low-energy -ray and neutron results of COMPTEL we determine the energy spectrum of the interacting protons in the 10-200 MeV range. We find that the COMPTEL data are consistent with a proton power law spectrum with index . To simultaneously fit the high-energy -ray measurements on board the GAMMA-1 satellite, the spectrum must steepen at a few hundred MeV and then become harder again to produce a detectable amount of GeV photons. Although the degree of steepening is composition dependent, the deduced spectrum of interacting protons is qualitatively invariant in the entire parameter region .
Key words: Sun: activity Sun: flares Sun: particle emission Sun: X-rays, gamma rays
This article contains no SIMBAD objects.
© European Southern Observatory (ESO) 1998
Online publication: November 3, 1998