Different Alfven wave acceleration processes of electrons in substorms at similar to 4-5 R-E and 2-3 R-E radial distance

Recent statistical studies show the existence of an island of cavities and enhanced electric field structures at 4-5 R-E radial distance in the evening and midnight magnetic local time (MLT) sectors in the auroral region during disturbed conditions, as well as ion beam occurrence frequency changes at the same altitude. We study the possibility that the mechanism involved is electron Landau resonance with incoming Alfven waves and study the feasibility of the idea further with Polar electric field, magnetic field, spacecraft potential and electron data in an event where Polar maps to a substorm over the CANOPUS magnetometer array. Recently, a new type of auroral kilometric radiation (AKR) emission originating from similar to2-3 R-E radial distance, the so-called dot-AKR emission, has been reported to occur during substorm onsets and suggested to also be an effect of Alfvenic wave acceleration in a pre-existing auroral cavity. We improve the analysis of the dot-AKR, giving it a unified theoretical handling with the high-altitude Landau resonance phenomena. The purpose of the paper is to study the two types of Alfvenic electron acceleration, acknowledging that they have different physical mechanisms, altitudes and roles in substorm-related auroral processes.