PPARCセミナー (2023/02/10)

PPARCセミナー 2023/02/10

発表者: 佐藤晋之祐 (M1)
タイトル: A Test Particle Simulation for the Jovian Magnetospheric Electrons Precipitating into Europa’s Oxygen Atmosphere
アブスト: Several observations using the Hubble Space Telescope (HST) reported that the brightness morphology of the oxygen OI] 135.6 nm emissions on Europa correlates with position of the moon with respect to the Jovian magnetospheric plasma sheet, which results in the north-south asymmetric aurora morphology. The north-south asymmetry of Io’s auroral limb glow has been explained by higher electron flux into the atmosphere on the hemisphere that faces the plasma sheet center. This explanation, however, has not yet been evaluated for the case of Europa quantitatively.In this study, we used a test particle simulation for the Jovian magnetospheric electrons to estimate the electron flux into Europa and the brightness of the 135.6 nm aurora in Europa’s atmosphere.The local electron flux from the Jovian magnetosphere to Europa’s surface is estimated on the order of 10^9 – 10^10 cm-2 s-1. The electron flux to the surface is lower where the magnetic field lines are tangential and higher where the field lines are perpendicular to the surface.Our results show that the systematically changing north-south asymmetry of the oxygen aurora at 135.6 nm is recreated with the previously suggested idea, where the strong deceleration of the entire magnetospheric plasma flux tube results in the inhomogeneous electron energy flux into the atmosphere. However, such artificial deceleration is not feasible in the Jovian magnetosphere, and thus there is some lack in the previous explanation on the north-south asymmetry of Europa’s oxygen aurora brightness.