Energetic electrons in the midlatitude nighttime E region

Abstract

Nike Apache 14.439 was launched from Wallops Island at 0003 EST on 1 November 1972, a very disturbed night (K sub P = 8). A Geiger counter in the payload detected electrons ( keV) with a maximum flux of 1086 + or -261/sq cm/sec/ster. The height-averaged ionization rate in the upper E region is calculated from the measured electron density profile and has a value of 35 1/cu/cm/sec. The ionization rate can be reconciled with the observed flux of electrons ( 70 2 keV) if the spectrum ( keV) is of the form J ( E) = J sub O exp(-E/E sub O) with E sub O equal to 8.3 keV. The ionization rate on this and other nights is found to be strongly dependent on geomagnetic activity. It is suggested that energetic electrons are the principal source of ionization at midlatitudes in the upper E region near midnight, even under rather quiet geomagnetic conditions