3:45 PM - 4:00 PM
[PPS01-08] Hot electron distribution in the Jovian inner magnetosphere derived from Hisaki and Juno
Keywords:Jupiter, Magnetosphere, Plasma
The behavior of Jupiter's magnetosphere is thought to be driven by plasma from Io's volcanoes, and comparison with the Earth's magnetosphere, which is driven by the solar wind, provides insight into magnetospheric structure on planets in general. Jupiter rotates at a higher speed than Earth, and the magnetic field lines co-rotate with Jupiter. Io has many volcanoes, and the gases generated by the eruptions become plasma in space, which is trapped by the co-rotating magnetic field lines in the magnetosphere, forming a torus-like plasma zone (Io-plasma torus: IPT). In Jupiter's magnetosphere, the magnetic field lines capture the plasma, increasing its mass, which is stretched by centrifugal force and transported outward, resulting in the inward flow of hot electrons in the inner magnetosphere and reconnection in the outer magnetosphere. Although there are observational facts that actually indicate these phenomena through ground-based and in-situ observations to date, the specific transport and acceleration mechanism of the Io-derived plasma and the interaction between Io's volcanic activity and the magnetosphere are unknown. To understand this transport mechanism, we believe that high-resolution and wide-area observations in the IPT to Jupiter's far regions are necessary.
In this study, we considered it necessary to obtain long-term electron distribution in order to clarify the plasma transport in Jupiter's inner magnetosphere. Therefore, we focused on two spacecraft, the HISAKI satellite and the Juno spacecraft. HISAKI remotely observes Jupiter and the IPT from Earth orbit with a nearly constant field of view. Juno is performing in-situ observations of Jupiter from the distant magnetosphere, which extends several tens of RJ (1RJ: one Jupiter radius) from Jupiter, to as close as 1~2 RJ (Perijove: PJ). We thought we could obtain complementary observations by combining the data from Juno, which passes near the IPT during PJ, and the data from HISAKI, which observes the IPT. The electron parameters are obtained by spectral fitting to the spectral data observed by HISAKI, and the complementary use of the observed electron energy distribution data obtained by Juno is expected to clarify the electron distribution change in the inner magnetosphere and to elucidate the transport mechanism. The high-temperature electrons obtained from the analysis of HISAKI were used to obtain the electron energy distribution data.
The high-temperature electron distribution obtained from the HISAKI analysis was compared with the average electron distribution above 50 eV obtained from the Juno analysis, and the trend that the high-temperature electrons increase with Jupiter's distance from the planet was consistent. In previous studies, the plasma transport in Jupiter's inner magnetosphere was inferred from far-field observations, but in this study, the analysis including direct observations shows that the two distributions show a similar trend. This has allowed us to obtain a more detailed electron distribution in Jupiter's inner magnetosphere and to show that the electron distribution may change due to factors such as Io's volcanic activity.
In this study, we considered it necessary to obtain long-term electron distribution in order to clarify the plasma transport in Jupiter's inner magnetosphere. Therefore, we focused on two spacecraft, the HISAKI satellite and the Juno spacecraft. HISAKI remotely observes Jupiter and the IPT from Earth orbit with a nearly constant field of view. Juno is performing in-situ observations of Jupiter from the distant magnetosphere, which extends several tens of RJ (1RJ: one Jupiter radius) from Jupiter, to as close as 1~2 RJ (Perijove: PJ). We thought we could obtain complementary observations by combining the data from Juno, which passes near the IPT during PJ, and the data from HISAKI, which observes the IPT. The electron parameters are obtained by spectral fitting to the spectral data observed by HISAKI, and the complementary use of the observed electron energy distribution data obtained by Juno is expected to clarify the electron distribution change in the inner magnetosphere and to elucidate the transport mechanism. The high-temperature electrons obtained from the analysis of HISAKI were used to obtain the electron energy distribution data.
The high-temperature electron distribution obtained from the HISAKI analysis was compared with the average electron distribution above 50 eV obtained from the Juno analysis, and the trend that the high-temperature electrons increase with Jupiter's distance from the planet was consistent. In previous studies, the plasma transport in Jupiter's inner magnetosphere was inferred from far-field observations, but in this study, the analysis including direct observations shows that the two distributions show a similar trend. This has allowed us to obtain a more detailed electron distribution in Jupiter's inner magnetosphere and to show that the electron distribution may change due to factors such as Io's volcanic activity.