Relationship between Pulsating Aurora and Small-scale Field-Aligned Current Systems

Abstract:

Field-aligned currents derived from CHAMP satellite overpasses were compared to THEMIS ground-based all-sky camera array. Two separate conjunctions were studied in detail. The primary focus of this study was to investigate FAC derived from magnetometer measurements obtained by CHAMP collocated with various auroral phenomena. Two types of aurora were studied in detail: pulsating aurora and diffuse aurora occurring equatorward ward of an established auroral arc. We found that pulsating aurora exhibited low levels of fluctuating field aligned currents alternating between +/− 1 μA/m² for the duration of the conjunction. We found similar behaviour for diffuse aurora equatorward of stable auroral arc events. Upon entering the region of diffuse aurora CHAMP recorded an alternating current fluctuating between +/− 5 μA/m². High resolution data confirmed this alternating current structure as well as the presence of small scale arc structure seen by larger, small time scale amplitude fluctuations similar to that seen in the auroral arcs. These results show that electrical currents in diffuse and pulsating auroral structures are relevant.