High-latitude dayside ionosphere response to Pc5 field line resonance

Abstract. We report observations of pulsations due to Field Line Resonance (FLR) in the morning sector of the high-latitude dayside ionosphere on 1 February 1998. The Geotail spacecraft, ideally skimming the dayside magnetopause, monitored the magnetopause motion, which is seen to induce a modulated response of the ionosphere by means of ULF waves. Pulsations in the Pc5 frequency range were observed in the ground magnetic field measured by the IMAGE array, as well as in the electron and ion temperatures measured by the EISCAT Svalbard Radar. The ion temperature oscillations are an indicator of a modulated convection electric field while field-aligned currents (FAC) associated with the FLR control the electron temperature. We have performed a simulation of the ionosphere experiencing sinusoidal FAC and electric field in order to confirm our hypothesis. In addition to the ionospheric response, the possible cause of the FLR and processes involved are also discussed.

Key words. Magnetospheric physics (MHD waves and instabilities; magnetosphere-ionosphere interactions) – Ionosphere (polar ionosphere)