Altitude profile of electron density and oxygen green line in active auroral arcs based on electron differential number flux observed by sounding rocket

• Main Authors: Kunizo Onda, Masaki Ejiri, Yukikazu Itikawa, Hiroshi Miyaoka
• Format: Report
• Language: English
• Published: Faculty of Industrial Science and Technology Science University of Tokyo 1998
• Subjects: Syowa Station; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4236; http://id.nii.ac.jp/1291/00004236/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4236&item_no=1&attribute_id=18&file_no=1

The Monte Carlo method was applied to investigate electron auroras observed by the sounding rocket S-310JA-8,which was launched on April 4,1984 from Syowa Station in Antarctica of the invariant latitude 66.14°S and the geomagnetic longitude 70.98°. The number density of the atmosphere, in which constituent elements were assumed to be N_2,O and O_2,and temperatures were estimated by the MSIS-86 model for the aurora observed there. A downward electron differential number flux was measured at the altitude of 200km, from which electrons were injected downward into the upper atmosphere. An initial electron energy E_0 is investigated in the range from 100 eV to 18 keV. An initial pitch angle was assumed to be uniformly distributed in the range of [0,π/2].Ionization rates of N_2,O and O_2 were calculated as a function of an altitude, the initial pitch angle, and the initial electron energy. The total ionization rate obtained by summing up individual ionization rate was considered to be a production rate of thermal electrons. A loss rate of thermal electrons was estimated by using an electron density and an effective recombination rate. Under the assumption of local equilibrium of ionization and recombination, the height profile of electron density was deduced and compared with the observed one. The height profile of an emission rate was also investigated for the oxygen green line. The emission rate calculated as contribution from the electron impact was compared with the one produced by the collision process N_2 (A^3Σ_u^+)+O(^3P), and it was made clear that the latter collision process was more efficient to excite oxygen atoms from O(^3P) to O(^1S) than the electron impact in the wide range of electron energy observed by the sounding rocket.