Investigation on the impact of solar flares on the Martian atmospheric emissions in the dayside near-terminator region: Case Studies

Abstract: Solar transient events like flares can cause sudden changes in planetary plasma and neutral environment. Here, we present an investigation of the variability of the Martian atmospheric emissions viz. OI 130.4 nm, 135.6 nm, CO2+ ultraviolet doublet (UVD), and CO Cameron band (CB) in the less explored dayside near-terminator region during solar flare events. The two X8.2 and M6 class flares during September 2017 on Mars have been selected from existing catalogs. Using data from the imaging ultraviolet spectrograph (IUVS) aboard the MAVEN spacecraft, we examined limb radiance profiles. We observed a significant increase in radiance for major emissions around the peak with a more pronounced impact below the peak during flares compared to quiet time. During solar flares, for 130.4 nm and 135.6 nm emission, the maximum deviation in radiance beneath peak approaches to ~63% and ~123%, respectively. Whereas, for CO2+ UVD and CO CB, it is ~64% and ~50%, respectively. Additionally, we have presented an average scenario of dayside near-terminator (SZA~70-90{\deg}) and observed a notable trend of higher percentage deviation for atomic emissions compared to molecular emissions during flares. Further, our analysis depicts a higher percentage deviation during X8.2 compared to M6 class flare. This study underscores that during flares, higher photoelectron impact and irradiance flux drive the production processes, leading to enhanced emissions. The case studies emphasize, for the first time, the significant influence of flares on the Martian dayside near-terminator region, advancing our deeper understanding the impact of varying solar flare intensities to the planetary atmosphere.