Work Description

Date: 11/24/21

Dataset Title: A 3D Physics-based Particle Model of the Venus Oxygen Corona: Variations with Solar Activity

Dataset Creator: Valeriy Tenishev

Dataset Contact: Valeriy Tenishev vtenishe@umich.edu

Funding: 80NSSC17K0728 (NASA)

Key points:

- The density of Venus' extended oxygen corona varies almost by order of magnitude during a solar cycle.

- Venus' extended oxygen corona was observed by the Pioneer Venus Orbiter (PVO) only at solar maximum conditions.

- Kinetic modeling successfully explains Venus's extended oxygen corona's temporal and spatial variability.

- The strong dependence of the oxygen density in the corona from solar conditions is consistent with the non-detection of the oxygen corona from Venus Express.

Research Overview:

Here are the results of an investigation of the variability of Venus' extended oxygen corona. For that, we employ a combination of a fluid model VTGCM for simulating Venus' ionosphere and thermosphere and kinetic model AMPS for modeling the source and transport of energetic hot O atoms in the thermosphere.

We have found a good agreement of the model results with PVO observations.

We also found that the oxygen density strongly depends on solar conditions and varies by order of magnitude over a solar cycle.

That explains why the extended oxygen corona was observed only at the solar maximum.

The result presented in this paper will be a part of a later study of the planet's interaction with the ambient solar wind, where the corona model would be used to calculate the mass loading coefficient.

The altitude distribution of hot O calculated for the solar maximum conditions agree well with the appropriate Pioneer Venus Orbiter result. The solar minimum result is an order of magnitude lower and consistent with the non-detection from Venus Express. As expected, the solar moderate case is between the two.

Methodology:

Because Venus has no substantial planetary magnetic field the fast-flowing solar wind plasma can propagate to regions close to the planet. Therefore, the distribution of thermal atomic oxygen in the thermosphere, hot oxygen in the corona, and the resulting pickup oxygen ions are essential for determining the overall interaction of the planet with plasma of the ambient solar wind. To investigate the effect that this interaction has on the plasma-exosphere-thermosphere system we have initiated a project where this coupled system will be examined using a combination of Venus Thermosphere General Circulation model (VTGCM), Adaptive Mesh Particle Simulator (AMPS) and Block Adaptive Tree Solar-wind Roe Upwind Scheme (BATSRUS) codes. Each of the employed codes covers a physical sub-domain such that the coupled combination of the codes self-consistently describes the studied environment. Here we describe the modeling of the oxygen corona using the VTGCM and the AMPS kinetic particle model. VTGCM produces a self-consistent calculation of the thermosphere/ionosphere, providing spatial distribution of the dominant species. That is further used in AMPSs modeling of Venus' exosphere (1) to specify the source of the newly created hot O atoms produced by dissociative recombination of O$_2^+$ ions and (2) to account for thermalization of these energetic oxygen atoms as they propagate in the upper thermosphere.

Instrument and/or Software specifications:

-The Adaptive Mesh Particle Simulator (AMPS) (description available at https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=AMPS)
-The BATS-R-US model is similarly briefly described at https://ccmc.gsfc.nasa.gov/models/modelinfo.php?model=BATS-R-US
-fluid model VTGCM

Files contained here:

1. vtgcm-solar-maximum.tar.gz: contains the numerical model of Venus? ionosphere/thermosphere calculated for solar minimum conditions

2. vtgcm-solar-mimnimum.tar.gz: contains the numerical model of Venus? ionosphere/thermosphere calculated for solar maximum conditions

3. vtgcm-solar-moderate.tar.gz: contains the numerical model of Venus? ionosphere/thermosphere calculated for solar moderate conditions

4. amps-solar-maximum.gz: contains the numerical solution model of Venus? corona calculated for the solar maximum conditions

5. amps-solar-minimum.gz: contains the numerical solution model of Venus? corona calculated for the solar minimum conditions

6. amps-solar-moderate.gz: contains the numerical solution model of Venus? corona calculated for the solar moderate conditions

Visualization software: Tecplot

Related publication(s): Tenishev, V. et al. Application of the {Monte} {Carlo} Method in Modeling Dusty Gas, Dust in Plasma, and Energetic Ions in Planetary, Magnetospheric, and Heliospheric Environments, JGR, 2021.