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.

Equations describing the flow of a Newtonian liquid on a rotating disk have been solved so that characteristic curves and surface contours at successive times for any assumed initial fluid distribution may be constructed. It is shown that centrifugation of a fluid layer that is initially uniform does not disturb the uniformity as the height of the layer is reduced. It is also shown that initially irregular fluid distributions tend toward uniformity under centrifugation, and means of computing times required to produce uniform layers of given thickness at given angular velocity and fluid viscosity are demonstrated. Contour surfaces for a number of exemplary initial distributions (Gaussian, slowly falling, Gaussian plus uniform, sinusoidal) have been constructed. Edge effects on rotating planes with rising rims, and fluid flow on rotating nonplanar surfaces, are considered.

Abstract. This paper, a review of the present status of existing models for particle acceleration during impulsive solar flares, was inspired by a week-long workshop held in the Fall of 1993 at NASA Goddard Space Flight Center. Recent observations from Yohkoh and the Compton Gamma Ray Observatory, and a reanalysis of older observations from the Solar Maximum Mission, have led to important new results concerning the location, timing, and eificiency of particle acceleration in flares. These are summarized in the first part of the review. Particle acceleration processes are then discussed, with particular emphasis on new developments in stochastic acceleration by magnetohydrodynamic waves and direct electric field acceleration by both sub-and super-Dreicer electric fields. Finally, issues that arise when these mechanisms are incorporated into the large-scale flare structure are considered. Stochastic and super-Dreicer acceleration may occur either in a single large coronal reconnection site or at multiple "fragmented" energy release sites. Sub-Dreicer acceleration requires a highly filamented coronal current pattern. A particular issue that needs to be confronted by all theories is the apparent need for large magnetic field strengths in the flare energy release region.

We present and analyze the first high-resolution hard X-ray spectra from a solar flare observed in both X-ray/ g-ray continuum and g-ray lines. Spatially integrated photon flux spectra obtained by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) are well fitted between 10 and 300 keV by the combination of an isothermal component and a double power law. The flare plasma temperature peaks at 40 MK around the time of peak hard X-ray emission and remains above 20 MK 37 minutes later. We derive the nonthermal mean electron flux distribution in one time interval by directly fitting the RHESSI X-ray spectrum with the thin-target bremsstrahlung from a double-power-law electron distribution with a low-energy cutoff. We find that relativistic effects significantly impact the bremsstrahlung spectrum above 100 keV and, therefore, the deduced mean electron flux distribution. We derive the evolution of the injected electron flux distribution on the assumption that the emission is thick-target bremsstrahlung. The injected nonthermal electrons are well described throughout the flare by a double-power-law distribution with a low-energy cutoff that is typically between 20 and 40 keV. We find that the power in nonthermal electrons peaks before the impulsive rise of the hard X-ray and g-ray emissions. We compare the energy contained in the nonthermal electrons with the energy content of the thermal flare plasma observed by RHESSI and GOES. The minimum total energy deposited into the flare plasma by nonthermal electrons, ergs, is on the order of the energy in the thermal plasma. 31 2.6 # 10 Subject headings: Sun: flares -Sun: X-rays, gamma raysThe time history of the flare emission in three energy bands is shown in Figure 1a. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) uses two sets of aluminum attenuators, known as thin shutters and thick shutters, to avoid saturating the detectors during large flares. The July 23 flare was observed in two attenuator states. The instrument was primarily in the A3 state, with both sets of attenuators in place. Early in the flare, before 00:26:08 UT, and late in the flare, after 00:59:21 UT, the instrument was in the A1 state, with only the thin shutters in place. There were also four brief periods during which the instrument switched from A3 to A1 and back to A3. These transitions in attenuator state are apparent in the time history of the lowest energy band in Figure 1a. The flux calibration is currently uncertain during these four brief periods, so these time periods appear as gaps in subsequent results derived from the data.We corrected the observed counts for pulse pileup and decimation (see Smith et al. 2002). Pulse pileup occurs at high count rates, with multiple photons recorded as a single photon with an energy equal to the sum of the energies of the individual photons. Decimation conserves onboard memory by recording only a fraction of the incident photons. Background counts were determined from the data by linearly interpolating between the background level...

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