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The horse‐collar aurora: A frequent pattern of the aurora in quiet times
Author(s) -
Hones E. W.,
Craven J. D.,
Frank L. A.,
Evans D. S.,
Newell P. T.
Publication year - 1989
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/gl016i001p00037
Subject(s) - quiet , collar , earth's magnetic field , geology , ionosphere , physics , magnetosphere , solar wind , geophysics , geodesy , astronomy , magnetic field , mechanical engineering , quantum mechanics , engineering
Reported here are DE 1 auroral imager observations of an auroral configuration which is given the name “horse‐collar aurora.” The horse‐collar pattern comprises the total area of auroral emissions from a single hemisphere and derives its name from the shape of the emitting area. The pattern is found in images recorded during quiet geomagnetic conditions and is possibly related to the theta aurora, another quiet time configuration of the auroras. This initial report of the DE 1 observations illustrates the horse‐collar aurora with a 2‐hour image sequence that displays its basic features and shows an example of its evolution into a theta‐like auroral pattern. The interplanetary magnetic field was northward during this image sequence and there is some evidence for IMF B y influence on the temporal development of the horse‐collar pattern. A preliminary statistical analysis found the horse‐collar pattern appearing in one‐third or more of image sequences recorded during quiet conditions; it did not appear during disturbed conditions. Further study is required to establish more fully the characteristics of the horse‐collar aurora and to determine its implications concerning solar wind‐magnetosphere coupling when the IMF B z is northward.