3:30 PM - 5:00 PM
[PEM15-P08] Effects of the pitch angle distribution of precipitating electrons on altitude profiles
of electron density: ELFIN satellite and EISCAT radar observations
Keywords:Energetic Electron Precipitation
Energetic Electron Precipitation (EEP) causes various phenomena such as auroral emissions and changes in the atmospheric composition through collisions with the neutral atmosphere. It is essential to understand how the precipitating electrons with various pitch angles ionize the atmosphere for quantitative understanding of the EEP's effect on the atmosphere. However, some fundamental processes, such as propagation in the atmosphere and the secondary electron production of precipitating electrons, are still poorly understood. Recently, the importance of the magnetic mirror effect for atmospheric ionization is suggested by numerical simulation in Katoh et al. [under review]. The purpose of this study is then to verify the results of the numerical simulation by investigating observationally the effect of the magnetic mirror force on the atmospheric ionization.
We used pitch angle data in an energy range of 50 - 7000 keV observed by ELFIN satellites, flying on near-identical orbits with small but variable time-separation, at an altitude of about 450 km above, and electron density data in an altitude range of 60 - 170 km observed by EISCAT Tromsø UHF/VHF radars. We found 42 events in which the ELFIN satellites passed within ±2 degrees latitude and ±5 degrees longitude of Tromsø [19.2E,69.6N]. The number of events with strong EEPs below 100 km altitude was 33. For the numerical simulations, we used the Monte Carlo particle transport simulation adopted by Katoh et al. This simulation shows how the magnetic mirror force affects the production of secondary electrons, especially backscatter ones. In this study, the numerical simulation was used to calculate the collision rates between precipitating electrons and the atmosphere. The electron pitch angle and energy distribution data observed by the ELFIN satellite over Tromsø were used as the incident particles in the simulation. Altitude profiles of the electron density were estimated from the obtained collision rates and compared with the distributions observed by the EISCAT radar.
In this presentation, we discuss the effect of the magnetic mirror force on the altitude profiles of electron density by comparing the results of the observation and the simulation.
We used pitch angle data in an energy range of 50 - 7000 keV observed by ELFIN satellites, flying on near-identical orbits with small but variable time-separation, at an altitude of about 450 km above, and electron density data in an altitude range of 60 - 170 km observed by EISCAT Tromsø UHF/VHF radars. We found 42 events in which the ELFIN satellites passed within ±2 degrees latitude and ±5 degrees longitude of Tromsø [19.2E,69.6N]. The number of events with strong EEPs below 100 km altitude was 33. For the numerical simulations, we used the Monte Carlo particle transport simulation adopted by Katoh et al. This simulation shows how the magnetic mirror force affects the production of secondary electrons, especially backscatter ones. In this study, the numerical simulation was used to calculate the collision rates between precipitating electrons and the atmosphere. The electron pitch angle and energy distribution data observed by the ELFIN satellite over Tromsø were used as the incident particles in the simulation. Altitude profiles of the electron density were estimated from the obtained collision rates and compared with the distributions observed by the EISCAT radar.
In this presentation, we discuss the effect of the magnetic mirror force on the altitude profiles of electron density by comparing the results of the observation and the simulation.