Observed trends in auroral zone ion mode solitary wave structure characteristics using data from Polar

High-resolution (8000 sample s(-1)) data from the Polar Electric Field Inst rument are analyzed for a study of ion mode solitary waves in upward curren t regions of the auroral zone. The primary focus of this study is the relat ions between velocity, maximum potential amplitude, and parallel structure width of these solitary waves (SWs). The observed SW velocities consistentl y lie, within error bars, between those of the H+ and O+ beams observed sim ultaneously by the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) instrum ent. In addition, there is a trend that SW amplitudes are smaller when SW v elocities are near the O+ beam velocity and larger when SW velocities are n ear the H+ beam velocity. These results are consistent with the observed io n mode SWs being a mechanism for the transfer of energy from the H+ beam to the O+ beam. A clear trend is also observed indicating larger amplitude wi th larger parallel spatial width. The results suggest that the observed sol itary waves are a rarefactive ion mode associated with the ion two-stream i nstability.