Simulation of auroral photoemission rate for the first negative band system of N+2 at λ427.8nm using electron differential number flux observed by the sounding rocket

• Main Authors: Kunizo Onda, Hiroshi Miyaoka, Yukikazu Itikawa, Masaki Ejiri
• Format: Report
• Language: English
• Published: Faculty of Industrial Science and Technology, Science University of Tokyo 1997
• Subjects: Syowa Station; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4201; http://id.nii.ac.jp/1291/00004201/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4201&item_no=1&attribute_id=18&file_no=1

Electron auroras observed by the sounding rocket S-310JA-8 are investigated by using the Monte Carlo method. The MSIS-86 model is employed to represent the atmospheric number density and temperature in the aurora observed at Syowa Station in Antarctica of the invariant latitude 66.14°S and the geomagnetic longitude 70.98°on April 4,1984. Only N_2,O and O_2 are taken into account as components of the atmosphere. Electrons are injected downward into the upper atmosphere at the altitude of 200km, at which a downward electron differential number flux was measured. An initial electron energy E_0 is considered in the range of 100eV to 18keV. It is assumed that an initial pitch angle is uniformly distributed in the range of [0,π/2]. Production and emission at λ427.8nm rates of the first negative band system of nitrogen molecular ions N^+_2 (B^2Σ^+_u) are calculated as a function of altitude, the initial pitch angle, and the initial electron energy. Time variation of the observed absolute intensity of this line is reasonably well reproduced by the Monte Carlo method combined with the measured electron number flux. The difference in the absolute intensities obtained by experiment and theory is 5% at the time X+216s. This confirms that the Monte Carlo method is applicable to simulate collision processes and the resulting production and emission rates in electron auroras. Some representative results of emission rates are also presented for oxygen green and red lines.