5-species MHD Study of Martian hydrogen loss and source

Ion outflow plays an important role in the long-term evolution of Marss atmosphere. Besides the three heavy planetary ions O+, O2+, and CO2+, the loss of planetary protons is also important since it could be related to the loss of water. To study planetary proton loss due to solar wind interaction, we improve the 4-species sing-fluid MHD model of Mars, to a 5-species MHD model so that the planetary proton and solar wind proton can be tracked separately in the model. Our model shows that the current planetary proton loss rate is much less than O+ loss, implying a significant contribution of other escape processes of neutral hydrogen. Simulation results also suggest that a significant amount of solar wind protons are being lost near the planet, indicating that the main source of hydrogen corona is charge exchange reactions between solar wind protons with neutral oxygen. Integrated proton-oxygen charge exchange source terms will be examined to confirm the hypothesis. We will also turn off the hydrogen-oxygen charge exchange reaction, to better understand their influence on the Martian ionosphere and ion escape rates. We also plan to examine the hydrogen loss and source for early Mars conditions to examine how different they are from current Mars.