Stereoscopic observations of solar flares made onboard the 2001 Mars Odyssey spacecraft and CORONAS-F satellite

The results of observations of solar hard radiation recorded by two spacecraft—2001 Mars Odyssey and CORONAS-F—which were located in the vicinity of Mars and Earth, respectively, are discussed. The HEND instrument, developed at the Space Research Institute of the Russian Academy of Sciences, recorded photons with energies ranging from 80 keV to 2 MeV, and the SPR and SONG instruments, developed at the Skobeltsyn Research Institute of Nuclear Physics of the Moscow State University, detected radiation in the energy interval from 15 keV to 100 MeV. The rising of the sunspot group 10486 in late October 2003, which had been observed from Martian orbit before it was seen from the Earth’s surface, is analyzed in detail. In this case, observations made from directions that differ by 24° showed a close-to-24 h advance for the detection of hard radiation of flares. Stereoscopic observations of M-class flares near the limb show that the overwhelming part of radiation with energies above 80 keV arises at heights that do not exceed 7–10 thousand km. Also reported are the results of observations of the powerful flare on August 25, 2001, by the two devices, which complement each other substantially. The processes resulting in the formation of high-energy radiation of solar flares are discussed.