Comparison of plasma sheet dynamics during pseudobreakups and expansive aurorae

Global auroral images and plasma sheet ion distributions and magnetic field data are examined for two intervals when the Ultraviolet Imager (UVI) onbo ard the Polar spacecraft was imaging the entire northern auroral oval and, at the same time, the Wind spacecraft was passing through the near-Earth pl asma sheet. On 26 July 1997, UVI recorded a series of brief, localized auro ral brightenings known as pseudobreakups. On 27 March 1996, UVI observed se veral global expansions of auroral activity. Large variations in the magnet ic field were observed by the Wind magnetometer, large velocity moments wer e derived from Wind ion measurements, and ions were accelerated to mega-ele ctron-volt energies during both types of activity. The plasma sheet dynamic s appear very similar during these two different types of auroral activitie s. Closer inspection of the ion distribution functions and energy spectra i ndicate that the plasma sheet dynamics need to be characterized kinetically . (C) 2001 American Institute of Physics.