COMPTEL Neutron Image of the Sun

A major capability of the COMPTEL instrument is that it can measure the energy of individual neutrons arriving at the Earth after their production in solar flares, while measuring simultaneously the gamma radiation from the same event. The neutrons detected by COMPTEL (of energy 20 to 100 MeV) provide complementary information to the gamma-ray measurements, and ultimately relate to the spectrum of energetic protons at the site of the solar flare.

This figure shows an "image" of the Sun obtained by mapping back to their origin the neutrons detected by COMPTEL following the solar flare of 15 June 1991. It represents the first image of an astrophysical source in particles other than photons.

During the onset of the June 15th flare the CGRO was on the dark, "night" side of the Earth, and it was not until 40 minutes after the impulsive phase of this event that COMPTEL was able to collect its first data. Analysis of the neutron data acquired indicates that neutron emission extended for over an hour, implying that energetic protons continued to interact at the flare site long after the impulsive phase had passed.

An image sequence of the long-duration gamma flare emission from the Sun has also been produced from COMPTEL data recorded for the solar flare of 15 June 1991.

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