Spacecraft surface charging effect of plasma in bi-Maxwellian distribution

In some cases, a description in terms of bi-Maxwellian distributions is a better mathematical description of space plasma than that in terms of single Maxwellian distributions. To investigate the spacecraft surface charging effect of plasma in bi-Maxwellian distribution, this paper established equilibrium equations of spacecraft surface charging based on kinetic theory of plasma. Considering the plasma particle parameters of bi-Maxwellian distribution, the unit capacitor of spacecraft, the secondary electron emission and photoemission, the expression of spacecraft surface charging potential of plasma in bi-Maxwellian distribution was carried out, and the time evolutions of surface charging potential was got. The research results show that the surface charging potential of plasma in bi-Maxwellian distribution is lower than the surface charging potential of plasma in single Maxwellian distribution, and the assumption of plasma in single Maxwellian distribution will lead an overestimation of surface charging. In the second distribution function of bi-Maxwellian distribution, ion is the main factor which affects the final equilibrium charging potential. The higher the density or the higher the temperature of plasma in bi-Maxwellian distribution, the longer the time which is required for charging potential attaining equilibrium. The unit capacitor only affects the time required for charging potential achieving equilibrium, and it has no influence on the final equilibrium potential.