Printed in Great Britain. Pergamon Press plc AURORAL AND PLASMA FLOW TRANSIENTS AT MAGNETIC NOON

• Main Authors: M. Lockwood, P. E. Sandholt, A. D. Farmer, S. W. H. Cowley, B. Lybekk, V. N. Davda
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1990
• Subjects: EISCAT; Spitzbergen
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.694.6597; http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/1990/70_Lockwoodetal_1990.pdf

Abstract-We present observations of a transient event in the dayside aurora1 ionosphere at magnetic noon. F-region plasma convection measurements were made by the EISCAT radar, operating in the beamswinging “Polar ” experiment mode, and simultaneous observations of the dayside aurora1 emissions were made by optical meridian-scanning photometers and all-sky TV cameras at Ny Alesund, Spitzbergen. The data were recorded on 9 January 1989, and a sequence of bursts of flow, with associated transient aurora, were observed between OX:45 and 11:00 U.T. In this paper we concentrate on an event around 09:05 U.T. because that is very close to local magnetic noon. The optical data show a transient intensification and widening (in latitude) of the cusp/cleft region, as seen in red line aurora1 emissions. Over an interval of about 10 min, the band of 630 nm aurora widened from about 1.5 ” of invariant latitude to over 5 ” and returned to its original width. Embedded within the widening band of 630 nm emissions were two intense, active 557.7 nm arc fragments with rays which persisted for about 2 min each. The flow data before and after the optical transient show eastward flows, with speeds increasing markedly with latitude across the band of 630 nm aurora. Strong, apparently westward, flows appeared inside the band while it was widening, but these rotated round to eastward, through northward, as the band shrunk to its original width. The observed ion temperatures verify that the flow speeds during the transient were, to a large extent, as derived