Extended Gamma-Ray Emission of Solar Flares

G. Rank, V. Schönfelder and J. M. Ryan

An exciting discovery during the last solar cycle was the existence of extended gamma-ray emission of solar flares. COMPTEL measured extended emission of the flares on 9, 11 and 15 June 1991 in the 2.223 MeV neutron capture line for several hours after the impulsive phase (1). The emission originates mainly from accelerated protons with energies of 10 to 100 MeV. The long-term time profiles for all three flares are shown in the figure below. Our results can be compared to data from other instruments, including measurements of gamma-rays at higher energies, hard X-rays and microwaves. The following main characteristics of the extended phase have been found:


1. Rank, G., 1997, 25th ICRC, SH 1.3.2

2. Ramaty R. & Mandzhavidze N., 1994, AIP Proc., 294, 26

3. Ryan, J. M. & Lee, M. A., 1991, Ap.J., 368, 316

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