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The universal time variation of geomagnetic activity
Author(s) -
Russell C. 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/gl016i006p00555
Subject(s) - earth's magnetic field , universal time , variation (astronomy) , geomagnetic secular variation , physics , local time , atmospheric sciences , geophysics , geodesy , geology , geomagnetic storm , astrophysics , magnetic field , mathematics , statistics , astronomy , quantum mechanics
Geomagnetic activity exhibits both annual and daily variations. We examine these variations in the Am index which was designed to provide an accurate measure of the Universal Time variation of geomagnetic activity. The dayside reconnection process can quantitatively account for the observed variation in both indices. Control of these variations by the angle of the flow relative to the dipole axis is weaker than control by reconnection.