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Magnetic impulses and associated optical signatures in the dayside aurora
Author(s) -
Mende S. B.,
Rairden R. L.,
Lanzerotti L. J.,
Maclennan C. G.
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i002p00131
Subject(s) - ionosphere , geophysics , physics , magnetopause , cusp (singularity) , field line , electron precipitation , interplanetary magnetic field , magnetosphere , sky , magnetic reconnection , flux (metallurgy) , geology , astrophysics , magnetic field , geodesy , solar wind , geometry , mathematics , materials science , quantum mechanics , metallurgy
We present five magnetic impulse events observed at South Pole and in the magnetically conjugate area at Iqaluit. The magnetic signatures recorded during these events appear to be similar to those discussed by several authors as possible ionospheric signatures of sporadic dayside reconnection via the flux transfer process. Coordinated ground‐based image‐intensified all sky camera data were acquired at South Pole during the events. The optical data show that prior to the onset of each of the events the dayside cusp aurora is several degrees poleward of the station, signifying event initiation on closed field lines. Overhead aurora appears at the onset of the magnetic event and precipitation seems to expand over a large region equatorward of the quiescent cusp aurora. As the event decays the aurora dies away and the quiescent dayside cusp aurora, in four out of five cases, returns poleward of the station. This morphology is inconsistent with the model in which the ground based signature of an FTE is caused by a field aligned current configuration moving over a ground station in the antisunward direction. The observations show temporal events which begin at or inside the boundary of closed field lines. These are consistent with sudden precipitation activity on flux tubes which were previously equatorward of the cusp/cleft boundary and which became temporarily disconnected (non‐dipolar).