The electron thermal structure in the dayside Martian ionosphere implied by the MGS radio occultation data. Issue 2 (25th February 2015)

• Record Type: Journal Article
• Authors: Cui, J.; Galand, M.; Zhang, S. J.; Vigren, E.; Zou, H.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 2(2015:Feb.)
• Page Start: 278
• Page End: 286
• Publication Date: 2015-02-25
• Subjects: Martian ionosphere -- Chapman theory -- electron temperature; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2014JE004726
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: We propose a revised Chapman model for the ionosphere of Mars by allowing for vertical variation of electron temperature. An approximate energy balance between solar EUV heating and CO2 collisional cooling is applied in the dayside Martian ionosphere, analogous to the method recently proposed by Withers et al. (2014). The essence of the model is to separate the contributions of the neutral and electron thermal structures to the apparent width of the main ionospheric layer. Application of the model to the electron density profiles from the Mars Global Surveyor (MGS) radio occultation measurements reveals a clear trend of elevated electron temperature with increasing solar zenith angle (SZA). It also reveals that the characteristic length scale for the change of electron temperature with altitude decreases with increasing SZA. These observations may imply enhanced topside heat influx near the terminator, presumably an outcome of the solar wind interactions with the Martian upper atmosphere. Our analysis also reveals a tentative asymmetry in electron temperature between the northern and southern hemispheres, consistent with the scenario of elevated electron temperature within minimagnetospheres. Key Points: The electron thermal structure modulates the width of the ionospheric layer The electron temperature is elevated near the terminator A hemispheric asymmetry in electron temperature is tentatively seen