CGRO observations of gamma-ray flares associated with ACE particle events

During the period in which the ACE spacecraft has been operating, the Compton Gamma-Ray Observatory (CGRO) has continued monitoring hard X-ray and γ-ray emission from the Sun, among other sources. The high-energy photons provide information about both the electrons, through bremsstrahlung continuum emission, and nuclei, through nuclear line emission, while they are still near the site of their acceleration. The question of the common origin of solar photons and particles is addressed through comparison of the photon observations with associated ACE events. Among many hard-X ray flares associated with particle events seen by ACE, three had particularly interesting spectra from the CGRO Burst and Transient Source Experiment (BATSE). Two, on 4 Nov. 1997 and 22 Nov. 1998, had very hard continuum spectra up to MeV energies. The third event, on 28 Nov. 1998, showed substantial 511-keV line emission, above the ever-present instrumental background; this could be due to the production either of short-lived positron emitters, such as 11C, or pions