Modeling the effects of an H₂ gas release on the equatorial ionosphere

Release of a chemically reactive gas such as H 2 into the ionospheric F region results in a depletion of the electron density. This is due to the high charge exchange rate between the dominant O + ion and the H 2 gas, with subsequent dissociative recombination of the product ions and electrons. We investigate the simulated response of the low‐latitude nighttime (dusk) ionosphere to a point release of H 2 gas by solving the coupled set of time‐dependent continuity equations for O + and the product ions OH + , H 2 O + , and H 3 O + , including the effects of production, loss, and transport of ionization. We find that a 5‐kg release at 300 km over the magnetic equator at 1930 LT produces a depleted electron density region 40 km wide 52 s after release. At the center the electron density is reduced 37% from its prerelease value. Releasing 20 kg at the same altitude produces a hole 60 km wide and a density reduction of 54%. Corresponding values for a 10‐kg release at 350 km are 65 km and a 51% reduction. We also calculate the flux tube electron content reduction and the Pedersen conductivity reduction capable of being produced by the chemical releases. A large depletion will produce a ‘bubble’ which will buoyantly rise through the ionosphere owing to a Rayleigh‐Taylor instability mechanism. For the three simulated releases of 5 kg at 300 km, 10 kg at 350 km, and 20 kg at 300 km the depletions in the electron content 276 s after release are 5.8%, 7.4%, and 11.8%, respectively. The corresponding reductions in the flux tube integrated Pedersen conductivity are 2.1%, 5.1%, and 4.3%. In addition, the H 2 releases produce optical emissions at 6300 Å from O(¹ D ) and 3060 Å from OH(²Σ + ) with intensities greater than 1 kR.