Numerical Simulation of Ionospheric Depletions Resulting From Rocket Launches Using a General Circulation Model

Abstract

AbstractRocket exhaust plumes have been observed to cause large‐scale depletions of ionospheric plasmas (“ionospheric holes”). In the F region, charge exchange reactions occur between O+ ions and exhaust species such as H2O, H2, and CO2 to form ions, which then undergo rapid dissociative recombination. The Global Ionosphere‐Thermosphere Model (GITM) was extended to include these chemical reactions and appropriate source terms to represent rocket exhaust plumes. The resulting model allowed for the detailed simulation of advection, diffusion, and chemical interactions of rocket exhaust gasses in the upper atmosphere. This model was applied to ionospheric depletions resulting from the launches of Jason‐3 and FORMOSAT‐5 on SpaceX Falcon 9 rockets from Vandenberg Air Force Base. Outputs from the model were compared with GNSS, ionosonde, and satellite Langmuir probe measurements. Simulation indicated that the FORMOSAT‐5 launch resulted in a far larger and longer‐lived ionospheric depletion than the Jason‐3 launch, consistent with observations. These differences resulted primarily from the deposition of exhaust gasses at higher altitudes in the former case, which resulted in longer residence times in the upper F region where ionospheric plasma was replenished more slowly. Simulation of the FORMOSAT‐5 launch reproduced the approximate size, shape, and motion of the observed ionospheric depletion, which reflected the advection and diffusion of the rocket exhaust gasses through the thermosphere.