Systematics in auroral energy spectra

Abstract

There is a systematic increase in the mean energy of auroral electrons as the total precipitated energy increases. The change in λ 4278 N2+ intensity from ∼50 R to ∼10 kR (i.e., IBC 2+) correlates better with the change in mean energy of the precipitating electrons than with the change in number flux. Nightside aurora that exhibit this property superimpose on a wide region of soft (≲1 kev) precipitation that extends from the equatorial boundary of aurora to well poleward of normal visible aurora. On the dayside, the soft ‘cusp’ precipitation generates the statistical oval, although there may be larger energy inputs equatorward of the oval.