Cosmic ray ionization of the Jovian atmosphere

Abstract

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 10 19 cm −3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 10 3 cm −3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH 4 + and C n H m + cluster ions, with n ⩾ 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere (M ∾ 10 18 to 10 20 cm −3) and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.