Comparisons of Polar satellite observations of solitary wave velocities inthe plasma sheet boundary and the high altitude cusp to those in the auroral zone

Characteristics of solitary waves observed by Polar in the high altitude cu sp, polar cap and plasma sheet boundary are reported and compared to observ ations in the auroral zone. The study presented herein shows that, at high altitudes, the solitary waves are positive potential structures (electron h oles), with scale sizes of the order of 10's of Debye lengths, which usuall y propagate with velocities of a few thousand km/s. At the plasma sheet bou ndary, the direction of propagation can be either upward or downward; where as at the leading edge of high altitude cusp energetic particle injections, it is downward. For these high altitude events, explanations based on ion modes and on electron modes are both examined, and the electron mode interp retation is shown to be more consistent with observations.