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We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between February 2002 and December 2006, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the GOES 1 -8Å band; (2) the total energy radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the SXR-emitting plasma; (4) the bolometric radiated energy over the full duration of the event; (5) the energy in flare-accelerated electrons above 20 keV and in flareaccelerated ions above 1 MeV; (6) the kinetic and potential energies of the coronal mass ejection (CME); (7) the energy in solar energetic particles (SEPs) observed in interplanetary space; and (8) the amount of free (nonpotential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in flare-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of flare-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the -2 -CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the flare-accelerated particles, and the hot thermal plasma.Subject headings: Sun: activity -Sun: coronal mass ejections -Sun: flares -Sun: particle emission -Sun: X-rays, gamma rays * In yy/mm/dd format. * * GOES start time (UT). 1 Radiated energy in the GOES 1 -8Å band. 2 Total radiated energy from the SXR-emitting plasma. 3 Bolometric radiated energy. 4 Peak thermal energy of the SXR-emitting plasma. 5 Energy in flare-accelerated electrons. 6 Energy in flare-accelerated ions. 7 CME kinetic energy in the rest frame of the Sun. 8 CME kinetic energy in solar-wind rest frame. 9 CME gravitational potential energy. 10 Energy in SEPs. 11 Nonpotential magnetic energy in the active region.† Behind-the-limb event. ‡Bolometric irradiance directly measured with TIM -see Table 2.

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We summarize Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) hard X-ray (HXR) and gray imaging and spectroscopy observations of the intense (X4.8) g-ray line flare of 2002 July 23. In the initial rise, a new type of coronal HXR source dominates that has a steep double-power-law X-ray spectrum and no evidence of thermal emission above 10 keV, indicating substantial electron acceleration to tens of keV early in the flare. In the subsequent impulsive phase, three footpoint sources with much flatter double-power-law HXR spectra appear, together with a coronal superhot ( MK) thermal source. The north footpoint and the coronal T ∼ 40 source both move systematically to the north-northeast at speeds up to ∼50 km s Ϫ1 . This footpoint's HXR flux varies approximately with its speed, consistent with magnetic reconnection models, provided the rate of electron acceleration varies with the reconnection rate. The other footpoints show similar temporal variations but do not move systematically, contrary to simple reconnection models. The g-ray line and continuum emissions show that ions and electrons are accelerated to tens of MeV during the impulsive phase. The prompt de-excitation g-ray lines of Fe, Mg, Si, Ne, C, and O-resolved here for the first time-show mass-dependent redshifts of 0.1%-0.8%, implying a downward motion of accelerated protons and a-particles along magnetic field lines that are tilted toward the Earth by ∼40Њ. For the first time, the positron annihilation line is resolved, and the detailed high-resolution measurements are obtained for the neutron-capture line. The first ever solar g-ray line and continuum imaging shows that the source locations for the relativistic electron bremsstrahlung overlap the 50-100 keV HXR sources, implying that electrons of all energies are accelerated in the same region. The centroid of the ion-produced 2.223 MeV neutron-capture line emission, however, is located ∼ away, implying 20 ‫ע‬ 6 that the acceleration and/or propagation of the ions must differ from that of the electrons. Assuming that Coulomb collisions dominate the energetic electron and ion energy losses (thick target), we estimate that a minimum of ∼ ergs is released in accelerated 1∼20 keV electrons during the rise phase, with ∼10 31 ergs in ions above 31 2 # 10 2.5 MeV nucleon Ϫ1 and about the same in electrons above 30 keV released in the impulsive phase. Much more energy could be in accelerated particles if their spectra extend to lower energies.

We characterize and catalog 30 solar eruptive events observed by the Fermi Large Area Telescope (LAT) having late-phase >100 MeV γ-ray emission (LPGRE), identified 30 yr ago in what were called long-duration gamma-ray flares. We show that LPGRE is temporally and spectrally distinct from impulsive phase emission in these events. The spectra are consistent with the decay of pions produced by >300 MeV protons and are not consistent with primary electron bremsstrahlung. Impulsive >100 keV X-ray emission was observed in all 27 LPGRE events where observations were made. All but two of the LPGRE events were accompanied by a fast and broad coronal mass ejection (CME). The LPGRE start times range from CME onset to 2 hr later. Their durations range from ∼0.1 to 20 hr and appear to be correlated with durations of >100 MeV solar energetic particle (SEP) proton events. The power-law spectral indices of the >300 MeV protons producing LPGRE range from ∼2.5 to 6.5 and vary during some events. Combined γ-ray line and LAT measurements indicate that LPGRE proton spectra are steeper above 300 MeV than they are below 300 MeV. The number of LPGRE protons >500 MeV is typically about 10× the number in the impulsive phase of the solar eruptive event and ranges in nine events from ∼0.01× to 0.5× the number in the accompanying SEP event, with large systematic uncertainty. What appears to be late-phase electron bremsstrahlung with energies up to ∼10 MeV was observed in one LPGRE event. We discuss how current models of LPGRE may explain these characteristics.

We report the detection of high-energy γ-rays from the quiescent Sun with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to cosmic ray cascades in the solar atmosphere, and extended emission from the inverse Compton scattering of cosmic ray electrons on solar photons in the heliosphere. The observed integral flux (≥100 MeV) from the solar disk is (4.6 ± 0.2[statistical error] +1.0 −0.8 [systematic error]) × 10 −7 cm −2 s −1 , which is ∼7 times higher than predicted by the "nominal" model of Seckel et al. (1991). In contrast, the observed integral flux (≥100 MeV) of the extended emission from a region of 20 • radius centered on the Sun, but excluding the disk itself, (6.8 ± 0.7[stat.] +0.5 −0.4 [syst.]) × 10 −7 cm −2 s −1 , along with the observed spectrum and the angular profile, are in good agreement with the theoretical predictions for the inverse Compton emission.

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