The East-West Brightening Dependence of Multiple Brightening Poleward-Moving Auroral Forms with the Interplanetary Magnetic Field By-Component

Poleward-moving auroral forms (PMAFs) are observed during dayside auroral oval expansions and also during periods when the oval is expanded. The interplanetary magnetic field (IMF) has a major influence on the evolution of a PMAF. This statistical study looks at PMAF2 events, which re-brighten as they move poleward. PMAF2 events begin with intensification at a spot on the dusk(E)/dawn(W) side of a pre-existing auroral arc, depending on the IMF By-component. If the IMF By>0, a pre-existing dayside auroral arc initially brightens on the far eastern edge. The brightening then spreads westward along the pre-existing dayside auroral arc before it begins to propagate poleward. For IMF By<0, a pre-existing dayside auroral arc initially brightens on the far western edge. The brightening then spreads eastward along the pre-existing dayside auroral arc before it begins to propagate poleward. The PMAF2 events are identified using all-sky camera data from the Kjell Henriksen Observatory, located in Longyearbyen, Norway.