Date of Award

8-2018

Document Type

Thesis - Open Access

Degree Name

Master of Science in Engineering Physics

Department

Physical Sciences

Committee Chair

Dr. H. Katariina Nykyri

First Committee Member

Dr. Xuanye Ma

Second Committee Member

Dr. Jeremy A. Riousset

Abstract

Electromagnetic interactions between Mars remnant crustal magnetic fields and solar and planetary ions lead to time and space variations of the ionosphere. In this work, we continue the investigations started by Riousset et al. [2013] and address the effect of chemistry on ion populations in the dynamo region, where ion dynamics are driven by collisions while electrons are still mostly magnetized. We adopt a mesoscale model to simulate dynamics of electrons and ions in the upper atmosphere (100–400 km). Our approach focuses on numerical studies using the Martian Multifluid Magnetohy drodynamic (MF-MHD) Model (M4). The dynamo is a region which varies in time and space due to the lack of a global planetary intrinsic magnetic field, the location of the remnant crustal fields, and the planetary rotation responsible for day/night transition and subsequent trans-terminator particle transfer. The time scales of atmospheric collisions, gyromotions, and chemical processes are discussed in detail to support the selection of relevant reactions for mesoscale studies of the dynamo regions. Several schemes are available in the referenced literature [e.g.,Najib et al.,2011;Brain et al.,2015;Dong et al.,2018], and the chemistry model developed as part of this work is based on Najib et al. [2011]. The improved model more accurately reflects changes in the population of planetary ions, which can alter the dynamo current, thereby also causing perturbations of the magnetic field. The MAVEN mission has shown the importance of ion escape in the Martian atmospheric loss, and previous modeling studies [e.g., Riousset et al., 2014] have shown that electrodynamics in the dynamo region may impact upward transport of ions from this region, supporting the need for further studies. This work shows that the inclusion of chemistry results in substantial changes of ion distributions. Furthermore, differences in the symmetry, strength an altitude range of the dynamo current are observed, likely stemming from the absence of a peak electron density region because of an unbalanced production/destruction of CO+ 2 .

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