Crustal magnetic field advection on Mars by ionospheric plasma flow

• Autor(a) principal: Isabela de Oliveira
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações do INPE
• Texto Completo: http://urlib.net/sid.inpe.br/mtc-m21c/2020/08.12.07.13

The planet Mars has unique magnetic features among the solar system bodies. Although the planet does not currently have an active dynamo that generates a global magnetic field, like Earth has, there are regions in its crust which are strongly magnetized. Some of these magnetic fields have magnitudes comparable to magnetic fields on Earth. Evidences suggest that the crustal magnetic fields on Mars are remanent signatures from a Martian dynamo that was active in the past. These strongly magnetized regions, above which mini-magnetospheres are formed, are what distinguishes Mars from the other planets of the Solar System. Like at Venus, the interactions between the solar wind and Mars are mostly dominated by the properties of its ionosphere. However, Mars mini-magnetospheres influence the ionospheric interactions, changing ionospheric parameters and disturbing or generating local and global ionospheric currents. In this work, we propose that the crustal magnetic fields of Mars not only interfere in the planets ionosphere, but that also the contrary can happen, i.e., the ionosphere can disturb the crustal magnetic fields. We specifically study whether the ionospheric flow is able to displace the crustal magnetic fields by advection, dragging them in the anti-solar direction, along the day-to-night flow of the ionospheric plasma. In order to identify advection of the magnetic fields on Mars, we perform statistical analyses using data from MAVEN and MGS spacecraft over long periods of time. MAVEN radial magnetic field data of the whole planet are selected for the dawn-side and the dusk-side of Mars and compared to a crustal magnetic field model, for altitude ranges between 200-1000 km. The results show evidences that the magnetic fields are displaced and the cause for the displacement is likely to be advection due to the ionospheric flow. We also use MGS radial magnetic field data to investigate the advection on small regions of the planet and with a higher spatial resolution. We compare day-side data to night-side data at the orbit altitude of 400 km. The displacement of the magnetic fields seems to be correlated to the distance from the magnetic field to the main patch of magnetization in the Southern hemisphere of the planet. In order to have a general idea of the forces involved in the advection of the magnetic fields, we compare the dynamic pressure of the ionospheric plasma flow to the magnetic pressure of the crustal magnetic fields. For this study, we use MAVEN magnetic field and ionospheric data between 200-1000 km and between 04:00-20:00 local times. The results indicate that the advection of the magnetic fields is likely to be more expressive at the terminator regions of the planet, above regions of weak magnetic field background, e.g., in the Northern hemisphere of Mars.