Arase Observation of Simultaneous Electron Scatterings by Upper‐Band and Lower‐Band Chorus Emissions

• Published in: Geophysical research letters 2021-07, Vol.48 (14), p.n/a
• Main Authors: Kazama, Y., Miyoshi, Y., Kojima, H., Kasahara, Y., Kasahara, S., Usui, H., Wang, B.‐J., Wang, S.‐Y., Tam, S. W. Y., Chang, T. F., Asamura, K., Matsuda, S., Kumamoto, A., Tsuchiya, F., Kasaba, Y., Shoji, M., Matsuoka, A., Teramoto, M., Takashima, T., Shinohara, I.
• Format: Article
• Language: English
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL093708

This study reports a relation between electron flux modulations and chorus emissions by using correlation analysis. On April 18, 2017, Arase observed an enhancement of electron fluxes and intensification of banded chorus emissions at the same time. A result of the analysis shows that both the upper‐band and lower‐band chorus emissions have good correlations with field‐aligned electron fluxes that satisfy their resonance conditions. This indicates simultaneous interactions with both the emission bands and electrons, resulting in electron pitch‐angle scattering toward the magnetic field direction. In addition, low‐energy electron fluxes in the perpendicular direction also show positive correlations with the chorus intensities, probably because the chorus emissions are modulated by a fluctuation of perpendicular low‐energy electron fluxes. Plain Language Summary Scientists have believed that pulsating auroras in the polar regions originate in precipitating electrons that are caused by a wave‐particle interaction in the magnetosphere. Recent observational studies show direct evidence that chorus waves near the magnetic equator scatter local magnetospheric electrons, which are then streaming along the field line down to the ionosphere to generate aurora pulsation in response to modulation of the chorus emissions. Chorus waves usually have two distinct frequency bands, that is, upper band and lower band, but it had not been investigated that how two emission bands interact with electrons. In this study, we analyzed Arase satellite's observation data and identified good correlations between field‐aligned electron fluxes and intensities of the upper‐band and lower‐band emissions. This result indicates that pitch‐angle scattering of electrons takes place by both chorus emission bands simultaneously. Key Points Arase observed intense banded chorus emissions near the magnetic equator simultaneously with an electron flux enhancement Parallel electron fluxes show good correlations with intensities of both the upper‐band and the lower‐band chorus waves The positive correlation indicates pitch‐angle scattering of electrons by the chorus waves toward the magnetic field direction