Evaluation of Mars’ turbopause altitude with radio occultation technique

Details

Supervisors

Dehant, Véronique ; Karatekin, Özgur

Faculty

Faculté des sciences

Degree label

Master [120] en sciences physiques, à finalité approfondie

Abstract

This master thesis explores the altitude of the turbopause on Mars using the radio occultation technique. The turbopause marks the boundary between the lower atmosphere, which is neutral and homogeneous, and the upper atmosphere, which is ionized and heterogeneous. It is generally located around 100 km in altitude. The altitude of the turbopause varies due to different processes in the atmosphere, with temperature changes being the main driver of these variations. This study focuses on how the turbopause altitude changes with the seasonal cycle, the day-night cycle and dust events. In this research, the turbopause altitude is identified using radio occultation as the altitude where the refractivity, after baseline fit correction, reaches zero beneath the peak electron density of the ionosphere. Refractivity is defined as the index of refraction of the medium (in this case, the atmosphere) minus one, meaning that zero refractivity corresponds to the refractivity of vacuum. The turbopause altitude is analysed over time, as well as by local solar time and latitude. However, due to variations in data comparability, particularly concerning differences in latitude and biases from correlations, conclusive results could not be drawn from the data selected for this study.