V.Izmodenov, Yu. Malama, A. Kalinin, M.Gruntman, R. Lallement, I. Rodionova

Hot neutral H in the heliosphere: elastic H-H, H-p collisions

Abstract. Williams et al.(1997) have suggested that a population of hot hydrogen atoms is created in the heliosphere through elastic H-H collisions between energetic ''solar'' atoms (neutralized solar wind) and interstellar atoms. They used a BGK-like approximation (Bhatnagar et al., 1954) for the Boltzmann collision term and the collision cross sections suggested by Dalgarno (1960). We show that both assumptions result in a significant overestimation of the the H-H collision effect. On the basis of calculated momentum transfer cross-sections for elastic H-H collisions, we argue that elastic H-H and H-p collisions cannot produce  hot H atoms in the heliosphere.