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.

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[1] Statistical results for the ionospheric outflows indicate that the ionosphere is an important source of plasma to the magnetosphere. However, the exact consequences on the dynamics of the magnetosphere from this ionospheric outflow have yet to be determined. This issue is taken up in multifluid modeling of the 24-25 September 1998 magnetic cloud event for which strong heavy ionospheric outflows have been previously reported. It is demonstrated that one of the key influences of heavy ionospheric outflows is to lower the cross-polar cap potential due to the mass loading it produces on the magnetosphere; i.e., the heavy ions provide a major sink for momentum that is transferred from the solar wind to the magnetosphere. The derived values for the cross-polar cap potential are shown to converge to that attained by assimilated mapping of ionospheric electrodynamics (AMIE) as the O + concentration at the ionospheric boundary is increased to $50% of the H

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Abstract. Mini-Magnetospheric Plasma Propulsion is a potentially revolutionary plasma propulsion concept that could enable spacecraft to travel out of the solar system at unprecedented speeds of 50 to 80 km s '1 or could enable travel between the planets for low power requirements of --1 kW per 100 kg of payload and ~ 0.5 kg fuel consumption per day for acceleration periods of several days to a few weeks. The high efficiency and specific impulse attained by the system are due to its utilization of ambient energy, in this case the energy of the solar wind, to provide the enhanced thrust. Coupling to the solar wind is produced through a large-scale magnetic bubble or mini-magnetosphere generated by the injection of plasma into the magnetic field supported by solenoid coils on the spacecraft. This inflation is driven by electromagnetic processes, so that the material and deployment problems associated with mechanical sails are eliminated.