The latitudinal variation of the charge exchange induced atomic hydrogen escape flux

Abstract

Using plasma data from the Isis 2 spacecraft and Arecibo radar, diffusive equilibrium models of the ionosphere were constructed for equinox conditions. These plasmaspheric models were combined with models of the neutral atmosphere to calculate the atomic hydrogen escape flux due to charge exchange between thermal protons and to calculate cooler hydrogen and oxygen atoms as a function of dipole latitude and local time. These calculations showed that the daytime escape flux increases as the absolute value of the dipole latitude decreases, reaching its maximum value at the magnetic equator. At 15 hours local time (LT) on March 23, 1972, the calculated escape flux varied from an insignificant amount at 55° dipole latitude, to 3 × 108 atoms cm−2 s−1 at the magnetic equator. In addition, the relative importance to the total charge‐exchange escape flux of the component due to charge exchange between protons and atomic oxygen is discussed. The contribution to the escape flux of plasma at high L values, and the effect of newly produced hot hydrogen upon the neutral temperature are also discussed.