Dayside auroral activity and magnetic flux transfer from the solar wind, Geophys

• Main Authors: M. Lockwood, P. E. Sandholt, S. W. H. Cowley
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1989
• Subjects: Lockwood; Todd; EISCAT
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.694.8570; http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/1989/49_Lockwoodetal_1989.pdf

Abstract. Combined observations by meridian-scanning photometers and the EISCAT radar show that the "midday-auroral breakup " phenomenon is associated with major increases in ionospheric flow. A sequence of nine events is observed in the early afternoon MLT sector during a period when the IMF is strongly southward with a large positive By component. Each auroral structure is seen at both 630 and 557.7nm and initially moves 1988). In addition, the emissions reveal particle acceleration to above solar wind energies, seemingly in both the cusp and the cleft regions. However, the relationship of the observed arcs to the isolated flux tube model of an FTE has been unclear. Radar observations provide a spatial grid of observations which Todd et al. (1986) and Lockwood et al. (1988b) have shown are consistent with poleward and eastward westward, accompanied by an increase in potential moving "isolated flux tubes", respectively. The of 30-60kV across the north-south dimension of the EISCAT field-of-view. After a few minutes the arc (or arc fragment) moves into the polar cap and fades, and the velocities observed by the radar swing from westward toward northward. We conclude that dayside auroral breakup is closely associated with momentum transfer across the magnetopause which occurs in a series of events 5-15 minutes apart. The largest of the observed events has dimensions of about 300km (in the direction of westward motion) by 700km, is bounded on its poleward edge by a 5kR arc and is associated with a potential of at least 80kV.