A global multispecies single‐fluid MHD study of the plasma interaction around Venus

Abstract

[1] This paper reports a new global multispecies single-fluid MHD model that was recently developed for Venus. This model is similar to the numerical model that has been successfully applied to Mars. Mass densities of proton and three important ionospheric ion species (O + , O 2 + , and CO 2 + ) are self-consistently calculated in the model by including related chemical reactions and ion-neutral collision processes. The simulation domain covers the region from 100 km altitude above the surface up to 24 R V in the tail. An adaptive spherical grid structure is constructed with radial resolution of about 5 km in the lower ionosphere. Bow shock locations are well reproduced for both solar-maximum and solar-minimum conditions using appropriate solar wind parameters for each case. It is shown that the shock locations are farther from the planet during the solar maximum condition, because of both the enhanced solar radiation strength and the relatively small Mach number. The simulation results also agree well with Venus Express observations, as shown by comparisons between model results with magnetic fields observed by the spacecraft.

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“…The latter is employed herein, and the neutral atmospheric profiles are based on the solar maximum conditions. The MS-MHD model solves a separate continuity equation for each ion species, and one momentum and one energy equation for the four ion fluids H Ma et al 2004Ma et al , 2013. In contrast to most global magnetosphere models applied to Earth that start from 2-3 Earth radii, the Mars/Venus MS-MHD model contains a self-consistent ionosphere, and thus the lower boundary extends down to 100 km altitude above the planetary surface.…”

“…The 3-D Block Adaptive Tree Solar-wind Roe Upwind Scheme (BATS-R-US) multi-species MHD (MS-MHD) model was initially developed for Mars (Ma et al 2004) and Venus (Ma et al 2013). The latter is employed herein, and the neutral atmospheric profiles are based on the solar maximum conditions.…”

“…and we will express all quantities in terms of the Venusian values detailed in Ma et al (2013), since the code was calibrated for Venus. The second parameter required as an input is the density at the base of the model, which requires the surface atmospheric pressure, p sur .…”

“…Case 2 (C2) corresponds to minimum P dyn and Ptot, but with the maximum Pmag. atmosphere from Ma et al (2013) is:…”

“…Although our final results are outwardly simple, we note that this interaction process is actually highly complex in nature. Our model self-consistently accounts for the ionospheric chemistries and electromagnetic forces (Ma et al 2004(Ma et al , 2013.…”