[1] It is widely accepted that the ionosphere is an important source of ions in the magnetosphere and until recently this population has largely been neglected from many global simulations. In this study, a causally regulated cusp O + outflow is added to the multifluid version of the Lyon-Fedder-Mobarry (LFM) global simulation. The cusp outflow algorithm uses empirical relationships to regulate the outflow flux with further conditioning to isolate the outflow spatially to a dynamic cusp. The impact cusp O + outflow has on the magnetosphere-ionosphere (MI) system is investigated for a moderate storm on 31 August 2005. It is found the MI system response depends upon the specification of the outflow velocity and temperature. More energetic outflow tends to flow downtail whilst colder, slower outflow fills the inner magnetosphere. High O + densities in the inner magnetosphere can increase the strength of the ring current, reducing Dst and inflating the magnetosphere. This effect is mostly found for the less energetic outflow specification. O + outflow is found to reduce the access of solar wind ions to the inner magnetosphere, which, through the MI coupling in LFM reduces the precipitating electron power, conductance and field-aligned currents. The effect outflow has on the cross polar cap potential (CPCP) depends upon two competing factors. The reduction in Region I currents when outflow is present appears to increase the CPCP whilst the inflation of the magnetosphere due to an enhanced ring current decreases the CPCP.

[1] A multifluid version of the Lyon-Fedder-Mobarry global simulation model has been used to investigate the effects of outflowing ionospheric O + on the magnetosphereionosphere system. To quantify these effects, we specify the number density, upward parallel velocity, and temperature of the O + outflow in a limited area of the low-altitude simulation boundary representing the projection of cusp, cleft, and low-latitude boundary layer. A baseline simulation without O + outflow is compared with simulations with a range of fluxes and initial velocities. In the cases with high fluxes, it is shown that the configuration of the magnetosphere is dramatically changed. In particular, the cross-polar cap potential is reduced, the polar cap area is increased, and the nightside reconnection line is moved earthward. Furthermore, in one case, the O + outflow leads to the onset of a second substorm not seen in the other simulation runs.

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.

A new 2‐D self‐consistent hybrid gyrofluid‐kinetic electron model in dipolar coordinates is presented and used to simulate dispersive‐scale Alfvén wave pulse propagation from the equator to the ionosphere along an L = 10 magnetic field line. The model is an extension of the hybrid MHD‐kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which also implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient magnetic field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the field line for the same magnitude perpendicular electric field perturbation.

A two-dimensional hybrid magnetohydrodynamic-kinetic electron model in dipolar coordinates is used to study the case of a fundamental mode toroidal field line resonance ͑FLR͒ centered on an L = 10 closed dipolar magnetic field line. The model is initialized via a perturbation of the azimuthal shear Alfvén velocity so that only upward field aligned currents ͑corresponding to downwelling electrons͒ are present at the ionospheric boundaries during the first half wave period. It is found that the acceleration of the electrons to carry the field aligned currents can be a significant sink of Alfvén wave energy depending on the width of the flux tube. For a FLR with an equatorial perpendicular wavelength of 0.25 R E about 20% of the wave energy is dissipated over a half cycle. This varies inversely with the width of the flux tube increasing to 40% by a width of 0.15 R E , which, unless the system is driven, can completely damp the resonance in about 2-3 cycles.

The ion temperature of the magnetosphere of Jupiter derived from Galileo PLS data was observed to increase by about an order of magnitude from 10 to 40 Jupiter radii. This suggests the presence of heating sources that counteract the adiabatic cooling effect of expanding plasma. There have been different attempts of explaining this phenomena, including a magnetohydrodynamic (MHD) turbulent heating model which is based on flux tube diffusion (Saur, Astrophys. J. Lett., 602, L137, 2004). We explore an alternate turbulent heating model based on advection, similar to models commonly used in solar wind heating. Based on spectral analysis of Galileo magnetometer (MAG) data, we find that observed MHD turbulence could potentially provide the required heating to explain some of the increase in plasma temperature. This indicates that advection is a more appropriate way to describe radial transport of plasma in the Jovian magnetosphere beyond 10 Jupiter radii.

[1] The generation of Alfvénic Poynting flux in the central plasma sheet and its polar distribution at low altitude are studied using three dimensional global simulations of the solar wind-magnetosphere-ionosphere interaction. A 24-hour event simulation (4-5 Feb 2004) driven by solar wind and interplanetary magnetic field data reproduces the global morphology of Alfvénic Poynting flux measured by the Polar satellite, including its dawn-dusk asymmetry. Controlled simulations show that the dawn-dusk asymmetry is regulated by the spatial variation in ionospheric conductance. The asymmetry disappears when the conductance is taken to be spatially uniform. The simulated Alfvénic Poynting flux is generated in the magnetotail by time-variable, fast flows emerging from nightside reconnection. The simulated fast flows are more intense in the premidnight sector as observed; this asymmetry also disappears when the ionospheric conductance is spatially uniform. Analysis of the wave propagation in the plasma sheet source region, near x GSM ≈ À15 R E , shows that as the fast flow brakes, a portion of its kinetic energy is transformed into the electromagnetic energy of intermediate and fast magnetohydrodynamic waves. The wave power is dominantly compressional in the source region and becomes increasingly Alfvénic as it propagates along magnetic field lines toward the ionosphere.

We have developed a hybrid magnetohydrodynamics (MHD) –kinetic box model valid for standing shear Alfvén waves using the cold plasma MHD equations coupled to a system of kinetic electrons. The guiding centre equations are used for the motion of the electrons and the system is closed via an expression for the field-aligned electric field in terms of the perpendicular electric field and moments of the electron distribution function. The perpendicular electric fields are derived from the ideal MHD approximation. We outline the basic model equations and method of solution. Simulations are then presented comparing the hybrid model results with a cold plasma MHD model. Landau damping is shown to heavily damp the standing shear Alfvén wave in the hybrid simulations when $v_{th} \ge V_{A}$. The damping rate is shown to be in good agreement with the theoretical rate calculated for the model parameters.