The Dependence of Mars Atmospheric Loss on Crustal Field Location: MAVEN Observation and Comparison with a MHD Model
Abstract
Our recent time-dependent MHD study suggests that the Mars crustal magnetic field acts as the primary internal driving force of variability in total planetary ion escape. In our global numerical simulation, we assume quiet solar wind conditions and consider the continuous local time change of crustal anomalies due to planetary rotation. Significant fluctuations of ~20% and ~50% are obtained during the entire rotation period for O+ and for O2+ and CO2+, respectively. From the MHD perspective, the control is exerted mainly through two processes. First, the crustal magnetic pressure over the subsolar regime controls solar wind penetration and mass loading and therefore the escaping planetary ion source. There is a strong negative correlation between the dayside magnetic pressure and ion loss with a significant time lag. Second, the crustal magnetic pressure near the terminator region controls the cross section area between the induced magnetospheric boundary and 100 km altitude at the terminator. The change in day-night connection regulates the extent to which planetary ions created in the dayside can be ultimately carried away by the solar wind and escape Mars. There is a strong positive correlation between the terminator crustal pressure and ion loss, with a shorter time lag. As the planet rotates, the dayside process and the terminator process work together to control the total amounts of escaping planetary ions. In the present work, we aim to test this theory by analyzing planetary ion escape observed by the SupraThermal and Thermal Ion Composition (STATIC) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The upstream solar wind plasma observation by the Solar Wind Ion Analyzer (SWIA) and IMF observation by Magnetometer (MAG) are used to provide an estimate of the external driving force of the Mars-solar wind interaction. We will examine the relationship between the MAVEN observed escaping planetary ion flux and Mars orientation to the Sun, and compare our finding with what we learn from the MHD model.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2015
- Bibcode:
- 2015AGUFM.P21A2087F
- Keywords:
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- 5405 Atmospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5421 Interactions with particles and fields;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5435 Ionospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5443 Magnetospheres;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS