Relative drift between black aurora and the ionospheric plasma

• Main Authors: E. M. Blixt, M. J. Kosch, J. Semeter
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Norway; Tromsø; EISCAT
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.210.284; http://www.ann-geophys.net/23/1611/2005/angeo-23-1611-2005.pdf

Abstract. Black auroras are recognized as spatially welldefined regions within uniform diffuse aurora where the optical emission is significantly reduced. Although a well studied phenomenon, there is no generally accepted theory for black auroras. One theory suggests that black regions are formed when energetic magnetospheric electrons no longer have access to the loss cone. If this blocking mechanism drifts with the source electron population in the magnetosphere, black auroras in the ionosphere should drift eastward with a velocity that increases with the energy of the precipitating electrons in the surrounding aurora, since the gradient-B curvature drift is energy dependent. It is the purpose of this paper to test this hypothesis. To do so we have used simultaneous measurements by the European Incoherent Scatter (EISCAT) radar and an auroral TV camera at Tromsø, Norway.