Pluto's ionospheric models and solar wind interaction

Chemical model calculations are carried out to describe the ion composition and density profile of Pluto's ionosphere. With the adopted surface pressure (approximate to 10 microbars) of the N-2 gas and the mixing ratio of CH4 (approximate to 7.4x10(-3)), the major ion is found to be H2CN+ and the peak ion number density is estimated to be about 3x10(3) cm(-3). If Pluto does not have an intrinsic magnetic field, the ionospheric penetration of the interplanetary magnetic field and solar wind plasma would be stopped at an altitude of about 1400 km because of collisional friction of the neutral atmosphere. (C) 2000 COSPAR. Published by Elsevier Science Ltd. All rights reserved.