Large-scale episodic enhancements of relativistic electron intensities in Jupiter's radiation belt

Abstract

Previous studies indicate that, in the Jovian magnetosphere, the long‐term trend of the radial profile of relativistic electron intensities is primarily shaped by slow radial diffusion. However, measurements by the Galileo spacecraft reveal the existence of transient increases in MeV electron intensities well above the ambient distribution. It is unclear how common such transient enhancements are, and to which dynamic processes in Jupiter's magnetosphere their occurrence is linked. We investigate the radial distributions of >11 MeV and >1 MeV electron intensities from 9RJ to 40RJ(RJ=71492 km denotes the Jovian radius), measured by the Galileo spacecraft from 1996 to 2002. We find transient enhancements of MeV electrons during seven Galileo crossings, mostly occurring around ∼20RJ. An apparent dawn‐dusk asymmetry of their occurrence is resolved, with a majority of events discovered at dawn. This dawn‐dusk asymmetry, as well as the average recurrence time scale of a few days, implies a potential relationship between the MeV electron transients and the storm‐like dynamics in the middle and outer magnetosphere detected using a variety of Galileo, Juno and remote sensing aurora observations. We suggest that the observations of some of these transients in the inner magnetosphere may result from a synergy between the convective transport by a large‐scale dawn‐dusk electric field and the sources provided by injections in the middle magnetosphere.

Jupiter's Whistler-mode Belts and Electron Slot Region

“…which is believed to be driven by the dawn-to-dusk electric field . Such a dawn-to-dusk electric field has also recently been utilized to explain the prompt acceleration of multi-MeV electrons at M > 14R J Yuan et al, 2021]. We suggest that the dawn-to-dusk electric field may also explain the higher flux and harder energy spectra observed by both Juno/JEDI (this study) and Galileo/EPD [Yuan et al, 2024] at dusk in comparison to the dawn flank.…”

Galileo Observation of Electron Spectra Dawn‐Dusk Asymmetry in the Middle Jovian Magnetosphere: Evidence for Convection Electric Field

“…Based on the solar wind propagation models (Tao et al., 2005; Zieger & Hansen, 2008), there is no obvious systematic difference of Pdyn before and after 2000 during the Galileo mission (Figure 8 of Yuan et al. (2021)). If the electric field implied here by the sub‐MeV electron spectra at M ∼ 15–20 was the outward extension of the one at IPT, then modulated by Pdyn variations, it was unlikely to enhance from 1996 to 2001.…”

Callisto's atmosphere and its space environment: prospects for the Particle Environment Package on board JUICE

“…In addition to the empirical models, we know that Callisto's orbital distance is in a region where large-scale charged particle acceleration events take place quite frequently. These have been observed both in energetic heavy ions, up to about 10 MeV/ nucleon (Selesnick et al, 2001) and in hundreds of keV to >10 MeV electrons (Yuan et al, 2021). The latter seem to develop more in the dusk and dawn regions of the magnetosphere, between 25 and 30 R J from the planet and with a recurrence of less than 1 week.…”