STUDIES ON THE INFLUENCE OF SOLAR FLARES ON THE MARTIAN ATMOSPHERIC EMISSIONS

Abstract

Understanding the dynamics of Mars atmosphere is crucial for unravelling the planets environment and climate evolution throughout the history. The Martian atmosphere exhibits significant variability in response to incoming solar radiation and solar transient events. These can cause major changes to the neutral and plasma environment of the Mars. However, there is a lack in understanding of the impact of these events specifically the solar flares on the Martian atmospheric emissions. This thesis aims to provide a thorough examination of how solar flares affect the four main atmospheric emissions found in the upper Martian atmosphere. The emissions considered in our studies are atomic oxygen - OI 130.4 nm and 135.6 nm, molecular emissions - CO2+ UVD (288-289 nm) and CO Cameron band (180-280 nm). The Imaging ultraviolet spectrograph (IUVS) onboard the MAVEN spacecraft data was utilized and a thorough analysis of the limb radiance profiles between ~ 80 and 180 km altitudes was carried out in this work. Our findings show that flares have a significant impact on the limb radiance profiles for all emissions, leading to increased brightness during flares compared to quiet periods, both at peak and below the peak region. The peak altitude however, was found to be stable. First, we performed a case study considering two solar flares i.e., 10 September 2017 (X8.2 class) and 17 September 2017 (M6 class) in the dayside near-terminator region. The impact of X8.2 class flare was found to be more prominent as compared to the M6 class flares in terms of radiance, electron flux, and solar irradiance flux. Atomic oxygen emissions (maximum for OI 135.6 nm) showed much higher deviation in peak radiance during event as compared to molecular emissions. The enhancements were explained using the collective effect of increased soft X-ray irradiance flux along with increased photoelectron flux. To further dig into the plausible mechanisms responsible for these enhancements, we explore the dependence of peak and lower altitude regions below the peak with respect to the SZAs, latitude, and longitudes. A strong dependence of the radiance has been observed with respect to the SZAs along with the latitudes. So, this thesis also sheds light on the importance of the photoelectron impact processes and solar incoming radiation flux in the atmospheric emissions during flares. Further, this study provides an overall scenario of the flare induced energy deposition on the Martian atmosphere during the declining and rising phase of the solar cycle and that eventually help to address the future exploration missions on Mars.