Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

P (Space and Planetary Sciences ) » P-CG Complex & General

[P-CG25] Planetary Magnetosphere, Ionosphere, and Atmosphere

Tue. May 28, 2019 10:45 AM - 12:15 PM A05 (TOKYO BAY MAKUHARI HALL)

convener:Kanako Seki(Graduate School of Science, University of Tokyo), Takeshi Imamura(Graduate School of Frontier Sciences, The University of Tokyo), Hiroyuki Maezawa(Department of Physical Science Osaka Prefecture University), Naoki Terada(Graduate School of Science, Tohoku University), Chairperson:Hiromu Nakagawa(Planetary Atmosphere Physics Laboratory, Department of Geophysics, Graduate School of Science, Tohoku University), Kanako Seki( Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo,)

11:30 AM - 11:45 AM

[PCG25-08] The influence of Martian crustal magnetic fields on atmospheric escape

*Dave A Brain1,2, Robin Ramstad1, Yaxue Dong1, Tristan Weber1, Shogo Inui2, Kanako Seki2, Andrew Poppe3, Riku Jarvinen4, Jim McFadden3, Jasper Halekas5, Jared Espley6, David Mitchell3, Laila Andersson1, Bruce Jakosky1 (1.University of Colorado, 2.University of Tokyo, 3.University of California Berkeley, 4.Finnish Meteorological Institute, 5.University of Iowa, 6.NASA Goddard Space Flight Center)

Keywords:Mars, Atmospheric escape, Magnetospheres

At present the influence of Martian crustal magnetic fields on atmospheric escape rates is debated. Since Mars lacks a significant global dynamo magnetic field, the presence of strong crustal fields over a significant fraction of the surface could shield portions of the atmosphere from the incident solar wind. The crustal fields could also allow or even enhance atmospheric escape through numerous cusp regions that are magnetically connected to the solar wind. This issue is of interest because the answer has implications for how atmospheric escape has operated on Mars over the history of the planet, including earlier times when Mars was more widely magnetized or even possessed a dynamo field. It is also relevant for assessing whether a global magnetic field is important for atmospheric retention. To this point, both modeling and observational studies appear to disagree on whether crustal fields significantly influence the escape of ions.

We will present the results of a new analysis of ion measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft mission made over four years. We examine how escape rates vary as Mars rotates and as a function of the solar zenith angle of strong crustal fields, including the dependence on ion energy and species. We also explore whether ion escape rates are larger, in a global sense, above crustal fields compared to non-magnetized regions. Finally, we introduce recent results relevant for evaluating ion escape from individual cusps, including from kinetic models of Martian cusp regions.