P/Halley ionosphere and spatial distribution of some constituents

The P/Halley ionosphere is investigated by data of the Three-Channel Spectrometer onboard VEGA 2 at the time of its last apparition in March 1986. Monochromatic composed images show the spatial distribution of ions from the heavy ion group—H2O+ (0,7,0), CO2+ B2Σu–X2Πθ band system and OH+. The OH and NH radicals are also studied for comparison (OH is the parent molecule of OH+ ion; the emissions of NH and OH+ are very close to each other). The integral intensities I in kR are plotted versus the projected distance to the nucleus p. found that the H2O+ ion has the strongest emission in comparison with the other ions. There is a peak at the nucleus and two jets. 2+ has a peaked structure and the maximal intensities are displaced from the nucleus towards the sun due to the recombination of CO2+ ions after reactions with neutral molecules. + spatial distribution has a peaked structure different from that of the NH radical. The OH composed image shows more uniform distribution than that of the OH+ ion. dial profiles of the ions are shown. Outside 5000 km the I(p) dependence can be approximated by 1/p. Maybe it is the transition of the ionopause. sults presented here can contribute to the study of the processes in the inner coma, or for improvement of the models of the solar wind–comet interaction in a small scale.