This paper presents the first comprehensive study of poleward moving auroral forms (PMAFs). PMAFs observed near the dayside auroral oval around geomagnetic noon have been the focus of many previous case studies. These ionospheric signatures are thought to be the product of solar wind‐magnetospheric interactions. This paper examines PMAFs using 12 years of ground‐based optical data from Longyearbyen, Svalbard. Examined are the distribution, lifetime, and time between successive PMAFs around geomagnetic noon. Changes in solar wind parameters are studied to see how they influence PMAF occurrence. The important results found from this study are (1) 15% of the PMAFs observed are PMAF1 events, 84% are PMAF2 events, and 1% are PMAF3 events, (2) PMAF1 events appear to favor slower solar wind speeds; higher solar wind speeds may lead to an increase of PMAF2 events, (3) PMAFs have a mean life time of 5 min, (4) the mean time between successive PMAF events is 6 min, (5) the PMAFs occur mostly for IMF Bz<0 conditions (117 PMAF events) but can also occur for steady IMF Bz>0 conditions (PMAF 41 events); another 31 PMAF events had an IMF Bz component, that when averaged was positive, (6) the distributions of successive PMAF events and that of inter‐FTE intervals are not different within a 95% confidence level, (7) there is a significant decrease in PMAF activity at geomagnetic noon, and (8) PMAFs are not likely to be caused by dynamic pressure variations in the solar wind.
Poleward moving transients have been proposed to be ionospheric signatures of plasma transfer events taking place at the dayside magnetopause. They are usually observed to brighten at the equatorward edge of the dayside auroral oval and fade as they move into the polar cap. This paper reports the observation of a new type of poleward moving dayside auroral transient which has several cycles of intensity variations. Observations of these transients show a series of intensifications in brightness along the arc or rayed band during poleward motion accompanied by a brightening in the auroral oval. As they reach their extreme poleward position they brighten and than fade from view. This brightening sequence may be explained by multiple reconnection of the magnetic flux tube associated with the transient.
Magnetic reconnection plays an important role in the magnetosphere‐ionosphere coupling and may lead to the formation of the dayside auroras. Observations of the dayside auroras may provide clues to the reconnection process at the magnetopause. Recently Fasel et al. [1992] observed poleward‐moving dayside auroral forms that rebrighten during their lifetimes. Lee et. al. [1993] examined the topology of magnetic flux ropes formed by the patchy multiple X‐line reconnection (PMXR), in which a magnetic flux tube reconnects with other flux tubes at multiple sites of limited extent. This paper develops the connection between the evolution of the magnetic flux ropes and the multiple brightenings of poleward‐moving dayside auroral forms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.