Double bursts inside a poleward‐moving auroral form in the cusp

Poleward‐moving auroral forms (PMAF), the ionospheric signatures of flux transfer events (FTEs), are intermittent phenomena observed in the cusp during negative interplanetary magnetic field intervals. Previous meridian scanning photometer‐based observations showed that the distribution of the separation time between successive PMAFs is maximum at ∼3.5 min. In this paper we present initial results from a new high‐sensitivity all‐sky imager, which was set up at Longyearbyen, Svalbard, Norway in October 2011. The 630.0‐nm all‐sky images taken with a time resolution of 4 s reveal that one of the PMAFs that occurred with such typical separation times on 29 December 2011 comprises two consecutive auroral bursts—the first occurring in the PMAF immediately after it was seen and the second, ∼2 min later, following almost the same route. This observation provides evidence that one PMAF could reflect double FTEs—there is not always a one‐to‐one correspondence between FTEs and PMAFs. Reconnection on the dayside magnetopause would be modulated with a period of ∼2 min during the course of transient reconnection.