“…The higher-frequency waves, due to instabilities such as the ion acoustic, are capable of heating the plasma [e.g., Boyd, 1977], but the applicability of this process is limited by the fact that the ion acoustic instability has a very high threshold unless T e >> T/. Nevertheless, these higher-frequency modes are still present at the shock when T e _• T i in the solar wind upstream from the shock [Rodriguez and Gurnett, 1976]. The lower hybrid modes, particularly the lower hybrid drift instability and the modified two-stream instability, on the other hand, are attractive because they heat both electrons and ions, are not suppressed when T e • T•, and have lower thresholds than the ion acoustic instability [Lemons and Gary, 1978].…”