Analysis of electron auroras based on the Monte Carlo method: Application to active electron are auroras observed by the sounding rocket as Syowa Station

摘要

A downward electron differential number flux, the absolute photoemission rate for the (0, 1) band of the first negative band system of the molecular nitrogen ion, and the number density of thermal electrons were simultaneously measured by the sounding rocket S-310JA-8 launched toward active auroral arcs at a substorm expansion phase on April 4, 1984, from Syowa Station in Antarctica. We apply the Monte Carlo method to analyze these observed results. The MSIS-86 model is employed to represent the atmospheric number density and temperature in the aurora observed by this experiment. Only N_2, O, and O_2 are taken into account as constituent elements of the atmosphere. Electrons are injected downward into the upper atmosphere at the altitude of 2-km, at which the downward electron differential number flux was measured. An initial electron energy is considered in the range of 0.1-18 keV. It is assumed that an initial pitch angle is uniformly distributed in the range of [0, #pi#/2]. Excitation and ionization rates of N_2, O, and O_2 are calculated as a function of altitude, the initial pitch angle, and the initial electron energy. Production and emission rates of the N_2~+ 1N (0, 1) band are deduced by using these calculated rates. Time variation of the observed absolute intensity of this band is reasonably well reproduced by the Monte Carlo method combined with the measured electron number flux.