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| INSTITUTET FÖR RYMDFYSIK | UPPSALA |
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| Swedish Institute of Space Physics | (59°50.272′N, 17°38.786′E) |
Student project (master level, 10c)/Studentprojekt (10hp)
Model-Observation Comparisons of O+ Concentrations in the Martian Ionosphere
Student: Chinmaya Nagar, Uppsala UniversitySupervisor: Erik Vigren
Period: Spring 2023
Abstract
A few years ago, the charge-transfer reaction CO2+ + O ⟶ O+ + CO2 was investigated experimentally for the first time since the study by Fehsenfeld et al., (1970). This new investigation was conducted by Tenewitz et al., (2018). The rate coefficient k < 6 × 10−13 cm3 s−1 , concluded by Tenewitz et al. (2018), differed substantially from the value of 9.6 × 10−11 cm3 s−1 reported by Fehsenfeld et al., (1970). Fox et al., (2021) showed that the old rate constants for the two channels of the CO2+ + O interaction work much better than the new ones in reproducing chemical features of the Martian ionosphere. Here, we combine MAVEN/NGIMS and TIMED/SEE data to conduct model-observation comparisons of O+ concentrations in the dayside Martian ionosphere. We consider each orbit of the MAVEN Deep Dip 2 (DD2) campaign between 17-22 April 2015. In the model, we balance the production rate of O+ through the aforementioned charge transfer reaction and the photoionisation of O and CO2 , with the loss rate through the reaction O+ + CO2 ⟶ O2+ + CO. We find a better level of agreement between the modelled and the observed O+ concentrations— (i) towards closest approach altitudes (∼ 130 km), and (ii) when using the old rate constant instead of the new one for the charge transfer reaction CO2+ + O ⟶ O+ + CO2 .Results
![[Mars]](../../img/mars_atm.jpg)
Maven above the Martian atmosphere [image credit: NASA]