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 T ownsend breakdown criterion is applied to the neutral gas of 10(17)-10 (20) m-3 surrounding the cylindrical spacecraft, which is assumed to h ave a highly negative potential with respect to the ionospheric plasma . Electrons are emitted from the surface and ionize the neutral gas in side the ionic sheath while they rotate around the spacecraft due to E x B drift. The Townsend coefficients of argon gas are calculated by M onte Carlo simulations based on the concept of equivalent reduced elec tric field. It is shown that the breakdown occurs in the range 200-100 00 V at neutral densities less than 10(19) m-3.