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) onboard the Polar spacecraft was imaging the entire northern auroral oval and, at the same time, the Wind spacecraft was passing through the near-Earth plasma sheet. On 26 July 1997, UVI recorded a series of brief, localized auroral brightenings known as pseudobreakups. On 27 March 1996, UVI observed several global expansions of auroral activity. Large variations in the magnetic field were observed by the Wind magnetometer, large velocity moments were derived from Wind ion measurements, and ions were accelerated to mega-electron-volt energies during both types of activity. The plasma sheet dynamics appear very similar during these two different types of auroral activities. Closer inspection of the ion distribution functions and energy spectra indicate that the plasma sheet dynamics need to be characterized kinetically. (C) 2001 American Institute of Physics.