Electron acceleration by dispersive scale Alfvén waves at Jupiter is investigated using a Gyrofluid‐Kinetic‐Electron model. Specifically, the simulations consider the propagation of an Alfvén wave perturbation from the center of the Io plasma torus to high‐latitude regions that are consistent with recent Juno satellite observations (e.g., Allegrini et al., 2017, https://doi.org/10.1002/2017GL073180; Mauk, et al., 2017a, https://doi.org/10.1038/nature23648; Mauk, et al., 2017b, https://doi.org/10.1002/2016GL072286; Szalay et al., 2018, https://doi.org/10.1029/2018JE005752). As in those observations, the energized electron spectra is broadband in nature and the majority of the energization is under the interaction of inertial Alfvén waves at high latitudes. The extent of the energization associated with these waves is proportional to both the magnitude of the wave perturbation and the ratio of the torus to high‐latitude density.

At Saturn's magnetopause, the shear flows are maximized (minimized) in the prenoon (postnoon) sector due to the rapid planetary rotation and the corotating magnetodisc. As such, the prenoon sector is expected to be more Kelvin‐Helmholtz (KH) unstable than the postnoon sector; however, in situ Cassini data analyses showed that the evidence of KH activity favors the postnoon sector. In this study, we use a two‐dimensional MHD simulation to demonstrate that fast‐growing KH modes strongly deform and diffuse the boundary layer on a time scale of a few minutes in the prenoon sector. Therefore, the KH observational signature is difficult to identify by spacecraft in the diffused boundary layer. KH vortices originating in the subsolar region (roughly from 10 to 14 local times) are transported to the postnoon sector and the wavelength is enlarged due to the gradient of shear flow, which is a plausible reason why KH events are more often observed in the postnoon sector. The prediction of the local boundary normal direction distribution as a function of spacecraft inward/outward crossing in the postnoon sector suggested by our simulation is qualitatively consistent with Cassini in situ observational results. We also discuss the impact of this dawn‐dusk asymmetric Kelvin‐Helmholtz evolution on magnetic reconnection at Saturn's magnetopause boundary.

Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally driven flux tube interchange instability, similar to the Rayleigh‐Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016, https://doi.org/10.1002/2015JA022122). We present a set of hybrid (kinetic ion/fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for the inner and middle magnetosphere at Jupiter and Saturn. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance requires only a temperature gradient as the magnetic pressure is constant. Pressure balance is achieved with a temperature gradient in a fixed magnetic field. The three‐dimensional simulation domain represents a local volume of the magnetodisc resonant cavity. Simulated RT growth rates compare favorably with linear theory, where the fundamental mode of the resonant cavity determines the largest (stabilizing) parallel wavelength. We suggest that the perpendicular scale of RT structures is determined by the fundamental mode, which limits growth due to magnetic tension. Finally, we investigated strong guide field magnetic reconnection and diffusive processes as plausible mechanisms to facilitate kinetic‐scale radial transport.