Based on magnetic field fluctuations, Saturn's magnetosphere can be divided into quiet (little or not much fluctuation) and disturbed periods (large fluctuation of the magnetic field). Kaminker et al. (2017, https://doi.org/10.1002/2016JA023834) showed that the average heating rate density of entire magnetosphere of Saturn is ∼10−17 W m−3 based on magnetic field fluctuations. Here, we categorize the magnetosphere of Saturn on the basis of magnetic field fluctuation. Using the eigenvalues of the variance analysis of the magnetic field, it has been found that the magnetodisc is in a disturbed state almost 6%–7% of the time. Dwell time normalization of the disturbed events suggests that most of the events happen at all latitudes between −5° and +30° and mostly on the dayside. Kinetic turbulent heating due to magnetic field fluctuation (δB) could potentially provide a significant amount of the required power.

A quantitative investigation of plasma transport rate via the Kelvin‐Helmholtz (KH) instability can improve our understanding of solar‐wind‐magnetosphere coupling processes. Simulation studies provide a broad range of transport rates by using different measurements based on different initial conditions and under different plasma descriptions, which makes cross literature comparison difficult. In this study, the KH instability under similar initial and boundary conditions (i.e., applicable to the Earth's magnetopause environment) is simulated by Hall magnetohydrodynamics with test particles and hybrid simulations. Both simulations give similar particle mixing rates. However, plasma is mainly transported through a few big magnetic islands caused by KH‐driven reconnection in the fluid simulation, while magnetic islands in the hybrid simulation are small and patchy. Anisotropic temperature can be generated in the nonlinear stage of the KH instability, in which specific entropy and magnetic moment are not conserved. This can have an important consequence on the development of secondary processes within the KH instability as temperature asymmetry can provide free energy for wave growth. Thus, the double‐adiabatic theory is not applicable and a more sophisticated equation of state is desired to resolve mesoscale process (e.g., KH instability) for a better understanding of the multi‐scale coupling process.

The motivation of this paper is to discuss the dynamical processes

Radial transport is an important dynamical process in Saturn's internally driven magnetosphere. Radial transport is presumed to occur by a centrifugally driven interchange instability, determined by the gradient of flux tube content and flux tube entropy. Plasma produced in the inner magnetosphere must be transported radially outward. The outward motion of the plasma stretches the magnetic field lines, leading to magnetic reconnection. Reconnection allows the mass to be transported radially while allowing the flux to circulate back to the inner magnetosphere. Both radial transport of mass and magnetic flux in Saturn's magnetosphere have been estimated based on Cassani Plasma Spectrometer data provided by Wilson et al. (2017, https://doi.org/10.1002/2017JA024117) and suggesting the radial transport rate of plasma of around 55 kg/s. The net magnetic flux transport should be 0, but the data suggest a net outward magnetic flux transport indicating the existence of different possible transport mechanisms in Saturn's magnetodisc.

One of the grand challenge problems of the giant planet magnetospheres is the issue of nonadiabatic plasma heating. Simple turbulent heating models consider the energy cascade rate from one scale to another where the energy density is based on perpendicular magnetic fluctuations of counterpropagating Alfvén waves. Analytical expressions from turbulence theory for the heating rate density have yielded promising results for the observed ion heating at Jupiter and Saturn. Here, we compare ion heating using hybrid simulations of the Kelvin–Helmholtz instability and analytical estimates in an effort to validate turbulence theory and further understand the nature of the ion heating. Heating rate densities ∼10−15 W/m3 are produced in our three‐dimensional Kelvin–Helmholtz simulations during the nonlinear growth phase and compare favorably with analytical estimates. Results targeting Saturn will be discussed in the broader context of radial plasma transport in the rapidly rotating magnetospheres.