Abstract
Diurnal curves of the average location of the equatorial edge of the auroral hydrogen oval (AHO) are presented for various levels of magnetic activity. Under absolutely quiet conditions this boundary is symmetrical about 23:15 corrected geomagnetic time (CGT), at which time it lies near 69.5° CG latitude. With increasing magnetic activity, it shifts equatorward and for Kp = 4 and 5 reaches 63° and exhibits a certain degree of asymmetry with its most equatorward position occurring at about 21:00 CGT. Isolated patches or luminous regions of hydrogenous aurora occasionally occur equatorward of the instantaneous equatorial boundary of the AHO, in a time interval extending from before 15:45 CGT (sunset) up to 00:30. Their occurrence has suggested that the polar pattern of auroral hydrogen emissions is composed of a permanent region which is commonly referred to as the AHO, and a temporary region, equatorward of it in the evening and afternoon where there occasionally can occur these patches of hydrogenous aurora.
Publisher
Canadian Science Publishing
Subject
General Physics and Astronomy
Cited by
1 articles.
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1. Auroral Structure and Dynamics;Dynamical and Chemical Coupling Between the Neutral and Ionized Atmosphere;1977