Global Electric Fields at Mars Inferred from Multifluid Hall-MHD Simulations

Abstract

In the Martian induced magnetosphere, the motion of planetary ions is significantly controlled by the ambient electric fields, which can be decomposed into three components: the motional, Hall, and ambipolar electric fields. Each of them is dominant in different regions and provides the ion acceleration with a particular effectiveness. Therefore, it is necessary to characterize the global distribution of these electric field components. In this study, a global multifluid Hall-MHD model is applied, which considers the motional, Hall, and ambipolar electric fields in ion transport and magnetic induction equations to self-consistently investigate the morphology of the electric fields in the Martian space environment. Numerical results suggest that the motional electric field is dominant in the upstream of the bow shock and in the magnetosheath along the Z MSE direction, leading to the formation of the ion plume escape channel. At the bow shock, the ambipolar electric field points outward, to decelerate and deflect the solar wind plasma flow. In the magnetosheath region, the ambipolar and motional electric fields with inward direction tend to reaccelerate the solar wind ions. However, along the magnetic pileup boundary, the Hall electric field pointing outward prevents the solar wind ions from penetrating the Martian induced magnetosphere, which also prevails in the Martian magnetotail region, to accelerate the ions’ tailward escape. This is the first systematic investigation of the global distribution of electric fields, which is helpful to understand the processes of ion acceleration/deceleration and escape within the Mars–solar wind interaction.

Acceleration of Pick‐Up Ions in the Martian Magnetosheath: A Tianwen‐1 Case Study

“…(2004) and Li et al. (2023), also presented a strong convection electric field in the magnetosheath, which is broadly consistent with the observations. Simulations also reveal the strongest convection electric field located near the MPB in the southern hemisphere, which is not captured by the observations.…”

“…Simulations also reveal the strongest convection electric field located near the MPB in the southern hemisphere, which is not captured by the observations. It was suggested that the strong convection electric field results from the increase in magnetic field due to pile‐up more than compensating for the decrease in flow velocity (Li et al., 2023).…”

Enhanced Oxygen Ion Outflow at Earth and Mars due to the Concurrent Impact of a Stream Interaction Region

“…This deep penetrating solar wind could be a source of ion energization in the dayside Martian ionosphere through direct energy and momentum transfer (Lundin et al 2004). Another major ion energization mechanism in the dayside ionosphere at this high altitude is the 'classical ion pickup' by solar wind motional electric fields and it dominates below <800 km where the solar wind velocity is high enough to accelerate the ions Li et al 2023). These electric fields can be produced due to the bulk motion of the magnetic field (Li et al 2023).…”

“…Another major ion energization mechanism in the dayside ionosphere at this high altitude is the 'classical ion pickup' by solar wind motional electric fields and it dominates below <800 km where the solar wind velocity is high enough to accelerate the ions Li et al 2023). These electric fields can be produced due to the bulk motion of the magnetic field (Li et al 2023). The heavy ions are energized to the keV range and will gyrate around the magnetic field lines with a huge gyroradius (∼30,000 km for O + ions) to reach higher altitudes .…”