Pc5 field line resonance frequencies and structure observed by SuperDARN and CANOPUS

Abstract

We have analyzed a number of low‐m Pc5 field line resonance events observed simultaneously by one or more of the Super Dual Auroral Radar Network (SuperDARN) radars and the Canadian Auroral Network for the OPEN Unified Study (CANOPUS) magnetometer array. At times there was excellent agreement in the Pc5 signal frequencies observed by radar and magnetometers. For events with good agreement in the measured signal frequencies, there was also reasonable agreement in the observed resonance positions and m numbers. Sometimes, however, the ordering of frequencies by their spectral power did not coincide between the radar and magnetometer data and even the frequencies of the spectral peaks did not always coincide. In these cases, there was also some apparent discrepancy in the observed resonance positions and m numbers. The resonance half power widths observed by the magnetometers were found to be a factor of 2 – 6 wider than those measured with the radar, owing to the spatial integration by ground‐based magnetometers of ionospheric current structures having scale size less than ionospheric height. Although there was general agreement in the direction of the longitudinal propagation, the m numbers obtained from the magnetometer data were found to be somewhat smaller that those calculated from the radar data. We consider and discuss possible reasons for the observed discrepancies.