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Intensification of preexisting auroral arc at substorm expansion phase onset: Wave‐like disruption during the first tens of seconds
Author(s) -
Liang Jun,
Donovan E. F.,
Liu W. W.,
Jackel B.,
Syrjäsuo M.,
Mende S. B.,
Frey H. U.,
Angelopoulos V.,
Connors M.
Publication year - 2008
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 - 10.1029/2008gl033666
Subject(s) - substorm , gyroradius , longitude , arc (geometry) , geophysics , geology , plasma sheet , phase (matter) , physics , geodesy , plasma , magnetosphere , instability , latitude , mechanics , geometry , mathematics , quantum mechanics
With the deployment of the all‐sky imager array of the THEMIS mission, we were able to construct a preliminary database of auroral substorm expansion phase onsets, from which we have established a number of common features characterizing the first tens of seconds of the substorm auroral intensification. We find that the intensification occurs within ∼10 sec over an arc segment extending approximately 1 h MLT and featuring wave‐like formations distributed in longitude. The longitudinal wave number ranges between 100 and 300 such that the wavelength is comparable to the ion gyroradius in the central plasma sheet. The scale the intensification is about 10–30 sec. This study casts important observational constraints on substorm onset theories.