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Session 70 - Solar Flares and Ejections.
Display session, Thursday, June 13
Tripp Commons,

[70.11] Extended \gamma-Ray Emission of the June 1991 Solar Flares

G. Rank, J. Lockwood, M. McConnell, J. Ryan, R. Suleiman (Univ. New Hampshire), V. Schönfelder (MPI f. Extraterr. Ph., Garching, Germany), K. Bennett (Astroph. Div., ESTEC, Noordwijk, The Netherlands)

The Compton-telescope COMPTEL is capable of measuring \gamma-rays in the energy range from 0.7 MeV to 30 MeV. During the solar flare events on 11 and 15 June 1991, COMPTEL detected extended emission in the neutron capture line for several hours after the impulsive phase.

Within the statistical uncertainty both flares show the same long-term behaviour. Their time profiles can be described by a double exponential decay with decay constants on the order of 10 min for the fast and 200 min for the slow component. In combination with measurements of other instruments our results allow us to rule out long-term trapping of particles in non-turbulent loops to explain the extended emission of these two flares and our data favour models based on continued acceleration.

For the June 11 flare, the spectrum during the extended phase is significantly harder than during the impulsive phase and pions are not produced in significant numbers before the beginning of the extended emission.

Program listing for Thursday