Rocket measurements of electron influx across the midday auroral oval

Abstract

A Black Brant IV rocket was flown through the dayside cusp from Cape Parry, N.W.T., (λ = 75°) on December 6, 1981. It flew to an apogee of 603 km and emerged into the polar cap at λ = 77°. The flight was through a fairly stable midday cusp at approximately 1230 magnetic local time. A very soft electron spectrum was observed, which was comparable with a Maxwellian distribution of E0 ≤ 10 eV. At energies above 100 eV, it was better fitted by a power law of form E−2. The energy flux was 0.2 erg∙cm−2∙s−1∙sr−1 (1 erg = 0.1 μJ), with most of this energy being deposited at heights below 400 km. The λ6300 emission intensity measured from the ground was about 1 kR, somewhat below average midday-cusp λ6300 intensity values. Three short intervals of electron energization were observed during the 11 min the rocket was within the cusp.