Impact of Superthermal Electrons in the Mars’ lower Ionosphere

Recent research has increasingly focused on understanding ion escape from Mars' ionosphere, a phenomenon that contributes significantly to atmospheric loss. Various models have emerged to explain the escape of charged particles from the Martian atmosphere, with one prominent explanation being the plasma expansion approach. This model suggests that the ionosphere undergoes continuous ion loss, with hundreds of tons of ions escaping daily. A key factor in this process is the presence of superthermal electrons in the lower Martian ionosphere, which have been observed to play a crucial role in enhancing plasma dynamics. The ionosphere of Mars is composed of three main positive ion species O_2^+,O^+ and CO_2^+ along with superthermal electrons, forming a complex plasma system. To investigate the ion loss processes, we model this system using a set of hydrodynamic fluid equations, incorporating the effects of superthermal electrons. The equations are reduced using a self-similar transformation, simplifying the problem into a set of ordinary differential equations. These equations are solved numerically to determine the plasma expansion characteristics, including ion density, velocity, and electric potential. Our study reveals the significant influence of superthermal electrons on plasma expansion, highlighting their role in enhancing ion escape and altering the plasma’s behavior. This approach provides new insights into the complex interactions within the Martian ionosphere and contributes to our understanding of atmospheric evolution on Mars.