CROSSED MAGNETIC-FIELD GAS-BREAKDOWN AROUND A CYLINDRICAL SPACECRAFT IN THE IONOSPHERE

Gas breakdown voltages are calculated for a cylindrical spacecraft in the ionosphere, whose axis is parallel to the geomagnetic field. The Townsend breakdown criterion is applied to the neutral gas of 10(17)-10(20) m-3 surrounding the cylindrical spacecraft, which is assumed to have a highly negative potential with respect to the ionospheric plasma. Electrons are emitted from the surface and ionize the neutral gas inside the ionic sheath while they rotate around the spacecraft due to E x B drift. The Townsend coefficients of argon gas are calculated by Monte Carlo simulations based on the concept of equivalent reduced electric field. It is shown that the breakdown occurs in the range 200-10000 V at neutral densities less than 10(19) m-3.