The COMPTEL Imaging Compton Telescope on-board the Compton Gamma Ray Observatory measured significant neutron and "/-ray fluxes from the solar flare of 9 June 1991. The "/-ray flux had an integrated intensity (> 1 MeV) of-30 cm-2, extending in time from 0136 UT to 0143 UT, while the time of energetic neutron emission extended approximately 10 minutes longer, indicating either extended proton acceleration to high energies or trapping and precipitation of energetic protons. The production of neutrons without accompanying "/-rays in the proper proportion indicates a significant hardening of the precipitating proton spectrum through either the trapping or extended acceleration process.
During the solar flare events on 11 and 15 June 1991, COMPTEL measured extended emission in the neutron capture line for about 5 hours after the impulsive phase. The 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. Within the statistical uncertainty both flares show the same long-term behaviour. 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. Our results with the measurements of others 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.
to 10 were significant microwave events with revealing multi-wavelength images of the flare environment. The event on September 10 was a large long-duration, gamma-ray flare (LDGRF). The event also produced a Ground Level Enhancement (GLE). Using the constraints from the microwave imaging data from the Expanded Owens Valley Solar Array (EOVSA) we interpret and model the behavior of the energetic-flare protons of September 10 as measured with the Large Area Telescope (LAT) on the Fermi mission. We do this in the context of stochastic acceleration in a large coronal bipolar structure to produce the high-energy long-duration gamma-ray emission. Our preliminary analysis suggests that the acceleration of the GeV protons takes place in a large structure about 1.4 R ☉ in length. The requirements for the magnetic field and turbulence in this structure will be presented.
The COMPTEL instrument onboard the Compton Gamma-Ray Observatory (CGRO) is sensitive to ),-rays in the energy range from 0.75 to 30 MeV and to neutrons in the energy range from 10 to 100 MeV.During the period of unexpectedly high solar activity in June 1991, several flares from active region 6659 were observed by COMPTEL. For the flare on June 11, we have analyzed the COMPTEL telescope data, finding strong 2.223 MeV line emission, that declines with a time constant of 11.8 minutes during the satellite orbit in which the flare occurs. It remains visible for at least 4 hours. We obtained preliminary values for the 2.2 MeV and 4-7 MeV fluences. Neutrons with energies above 20 MeV have been detected and their arrival time at the Earth is consistent with the v-ray emission during the impulsive phase. ~TRODUCTIONCOMPTEL is a useful instrument for studying solar flares. It is able to measure V -rays in the energy range from 0.75 MeV to 30 MeV and to derive the direction of the incoming radiation. When operating in its full-telescope mode, COMPTEL uses a double scattering of a v-quantum to get spectral and directional information. In this case, Compton scattering of the ),-ray is the fundamental process.
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