Three-dimensional modeling of barium cloud's expansion in the E and F regions: Applying for BROR mission.

The chemical release at an ionospheric altitude allows us to investigate the plasma processes in the ionosphere-magnetosphere system. The numerical models of the expansion of the artificial plasma clouds produced by the chemical release have been developed. Previous works revealed that, for a barium release with no directional velocity in the uniform background, the neutral barium cloud expands radially, while the ionized barium (Ba+) cloud produced by photoionization of the neutral cloud expands into an elliptic structure along the direction of the magnetic field. And they also revealed that the background ionospheric and initial release conditions primarily affect the cloud’s behavior. Barium Release Optical and Radio rocket (BROR) mission plans to conduct several barium releases at different ionospheric altitudes between 120 and 180 km, which are much lower than past experiments, aiming to study small-scale processes and structure in the auroral ionosphere by means of an active modification of the ionosphere. Since the atmospheric composition of ion and neutral spices and their parameters vary significantly around the BROR target region, i.e., from the E region to the bottom of the F region, we took into these altitudinal differences in our model. We revealed that the altitudinal difference contributes significantly to the Ba+ cloud’s expansion, especially with no background and release velocity, producing a teardrop shape. We also found that the Ba+ cloud at lower altitudes expands slowly, confining to a relatively small area due to the higher collision frequency. In comparison, the Ba+ cloud at a higher altitude stretches faster along the magnetic field and ends up with larger radii due to the lower collision frequency and higher diffusion rate. In this presentation, we show numerical results for the different release conditions at several altitudes in the E and F region and discuss the effects of different release conditions at various altitudes.