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We present a compilation of data for all 258 gamma-ray Ñares detected above 300 keV by the Gamma Ray Spectrometer (GRS) aboard the Solar Maximum Mission satellite. This gamma-ray Ñare sample was collected during the period from 1980 February to 1989 November ; covering the latter half of the 21st solar sunspot cycle and the onset of the 22d solar sunspot cycle. We describe the SMM/GRS instrument, its in-orbit operation, and the principal data reduction methods used to derive the gamma-ray Ñare properties. Utilizing measurements for 185 Ñares that were sufficiently intense to allow the derivation of gamma-ray spectra, we present an atlas of time proÐles and gamma-ray spectra. The Ñare parameters derived from the gamma-ray spectra include bremsstrahlung Ñuence and best-Ðt power-law parameters, narrow nuclear line Ñuence, positron annihilation line Ñuence, neutron capture line Ñuence, and an indication of whether or not emissions greater than 10 MeV were present. Since a uniform methodology was adopted for deriving the parameters, this atlas should be very useful for future statistical and correlative studies of solar Ñares. Subject headings : catalogs È gamma rays : bursts È Sun : Ñares 409 410 VESTRAND ET AL.Vol. 120

The ability of the tristatic UHF radar of EISCAT to measure plasma velocities in the F region has been employed for the assessment of such motions in the proximity of and relative to auroral arcs. This required real‐time tracking of the arcs with the radar upon command from the ground station monitoring the aurora. Slow relative motions of arc and plasma of the order of 30‐90 m s−1 were deduced from the observations, but the error sources are considerable. Three cases are presented, representing different situations. The arc may move into an auroral current system or out of it. The first case corresponds to an energy reduction, the second to a buildup of the energy content of the current system. Oscillatory motions, alternating between these situations, exist. The oscillations lie in the Pc 5 range and testify for an interaction of the energy release region (auroral acceleration region) and the generator via shear Alfvén waves. The events are interpreted in the light of the “fracture model” of auroral arcs developed by the first author. Although relative motions of the observed magnitude are predicted by this theory, other explanations are conceivable.

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