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Electron densities and temperatures in the Martian ionosphere: MAVEN LPW observations of control by crustal fields
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.ORCID iD: 0000-0002-7933-0322
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Leicester, Sch Phys & Astron, Leicester, England..ORCID iD: 0000-0002-6308-7890
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.ORCID iD: 0000-0003-2926-6761
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2023 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, no 3, article id e2022JA031027Article in journal (Refereed) Published
Abstract [en]

Mars Express and Mars Atmosphere and Volatile Evolution (MAVEN) observations have demonstrated the influence of Mars's spatially variable crustal magnetic fields upon the configuration of the plasma in the ionosphere. This influence furthermore leads to variations in ionospheric escape, conceivably in part through the modification of the plasma density and electron temperature in the upper ionosphere. In this study, we examine MAVEN Langmuir Probe and Waves data, finding a clear correspondence between the structure of the crustal fields and both the measured electron temperatures and densities, by first constructing an "average " profile from which departures can be quantified. Electron temperatures are shown to be lower in regions of strong crustal fields over a wide altitude range. We extend previous analyses to cover the nightside ionosphere, finding the same effects present to a lesser degree, in contrast to previous studies where the opposite relationship was found between densities and crustal fields. We further determine the altitude range over which this coupling between both plasma density (and temperature) and crustal fields is effective and use measurements made by MAVEN in the solar wind to explore the dependence of this crustal field control on the coupling to the solar wind and the interplanetary magnetic field (IMF). Based on this, there is some suggestion that variations in the solar wind dynamic pressure are associated with modulation of the effects of the crustal fields on plasma density, whereas the strength of the IMF modulates the crustal fields effects on both electron densities and temperatures.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2023. Vol. 128, no 3, article id e2022JA031027
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-481217DOI: 10.1029/2022JA031027ISI: 000934590000001OAI: oai:DiVA.org:uu-481217DiVA, id: diva2:1685940
Funder
Swedish National Space Board, DNR 156/16Available from: 2022-08-06 Created: 2022-08-06 Last updated: 2023-03-13Bibliographically approved
In thesis
1. The induced magnetospheres and magnetotails of Mars and Venus
Open this publication in new window or tab >>The induced magnetospheres and magnetotails of Mars and Venus
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this work we focus on several aspects of the ionospheres, induced magnetospheres, and magnetotails of the unmagnetized planets Mars and Venus. The solar wind interaction with unmagnetized planets differs from the magnetized planets: they are more directly exposed to the solar wind, and consequently can respond faster and more dynamically to solar wind variations, necessitating careful analysis of the driving conditions upstream simultaneously with plasma measurements in the system. This thesis is a compilation of an introductory part, and four articles. Three examine the ionosphere and the induced magnetosphere of Mars, while the last one investigates the properties of the induced magnetotail of Venus. Data from ESA’s Mars Express (MEX) and NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) missions are used in the Mars studies, while measurements from the two first Venus flybys of ESA’s Solar Orbiter (SolO) mission are used in the final paper. In our first study we investigate the nightside ionosphere of Mars using measurements from special high altitude operations of the ionospheric radar on board MEX. We find a consistent presence of plasma in the terminator region and we observe for the first time escaping plasma structures at solar zenith angles (SZAs) up to ~180 degrees at these high altitudes. The second project is a two-spacecraft statistical study where we use truly simultaneous observations from MEX in the induced magnetosphere of Mars and from MAVEN in the solar wind. Our aim was to investigate the response of the Martian induced magnetosphere to upstream conditions, and we find that even though stronger magnetic fields are observed in the induced magnetosphere for intervals of high solar wind dynamic pressure, when we compare these fields with the IMF magnitude the resulting ratio is actually enhanced during low pressure intervals, indicating the “volume” of the solar wind interacting with Mars is in fact larger in this situation. In the third study we investigate the correlation between electron densities and temperatures with crustal fields, and show the influence of the solar wind and IMF on this relationship. Finally, in our last study we observe the distant induced magnetotail of Venus, a region not well explored, through electron density and magnetic field observations from the first two SolO Venus flybys and compare with a global hybrid simulation. Together, this thesis expands our understanding of the plasma structures and dynamics of induced magnetospheres and magnetotails, using unique spacecraft data sets. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 69
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2173
Keywords
Mars, Venus, Ionosphere, Induced Magnetosphere, Induced Magnetotail
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-481218 (URN)978-91-513-1565-2 (ISBN)
Public defence
2022-09-27, Eva von Bahr 10K1190, Lägerhyddsvägen 1, 752 37 (Ångströmlaboratoriet), Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2022-09-05 Created: 2022-08-06 Last updated: 2022-09-05

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Andrews, David J.Stergiopoulou, KaterinaEriksson, Anders

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