Simultaneous Observation of Poleward-Moving Auroral Forms at the Equatorward and Poleward Boundary of the Auroral Oval

Poleward moving auroral form (PMAF) is a type of daytime auroral pattern, which is frequently seen in all-sky imager and meridian scanning photometer data. Characteristic of a PMAF is its separation from the auroral oval and subsequent poleward motion. It is widely believed that PMAFs occur more often during periods with dominant southward IMF, hence they are associated with flux transfer events (FTEs) and with reconnection at the subsolar point. However, most ground-based observing stations capable of dayside optical observations are near magnetic latitudes around 75 degrees, close to the equatorward boundary of the dayside auroral oval. Thus, PMAFs occurring at the poleward boundary might have been missed. In this study, we look at all-sky images from two stations, AGO-P1 and South Pole station, located on the same magnetic meridian in Antarctica at 80 and 74 degrees magnetic latitude, respectively. These two stations provide a broad view of the dayside auroral activity at both the equatorward and the poleward boundary of the auroral oval. Using the IMF data from one of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, we found that the tight relationship between PMAF and southward IMF is heavily biased by where the observations are made. The occurrence rate of PMAFs is 1:1 during northward and southward IMF at P1, the station at the poleward boundary of the auroral oval, whereas a significant increase in PMAF-s during southward IMF condition is shown at South Pole, the station at the equatorward boundary. The relationship between cusp aurora and PMAFs will be discussed. In addition, the simple reconnection model and the mechanism related to FTEs will be revisited based on our observations.