DAYSIDE POLEWARD MOVING AURORAL FORMS - A STATISTICAL STUDY

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 B-z < 0 conditions (117 PMAF events) but can also occur for steady IMF B-z > 0 conditions (PMAF 41 events); another 31 PMAF events had an IMF B-z 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.