Rocket-induced Daytime Midlatitude Plasma Depletions Observed by Swarm Constellation

The occurrence of ionospheric daytime midlatitude plasma depletions (DMLPDs) is a rare phenomenon because of the expected refilling of plasma depletions by photoionization during daytime. A SpaceX Falcon 9 rocket delivered an Earth observation satellite to orbit from Vandenberg Air Force Base in California at 18:51 UT on 24 August 2017. About 58 min after the rocket launch, DMLPDs were detected near the launch site by Swarm A and Swarm C satellites, i.e., the lower pair of the Swarm constellation. These DMLPDs were observed at an altitude of about 470 km (above the ionospheric F2 peak) within 25°N-40°N geographic latitude, corresponding to approximately 30.7°N-45.5°N geomagnetic latitude. The formation of these DMLPDs is difficult to explain in association with natural phenomena. The appearance of these DMLPDs near the launch station (with a geographic longitude separation of about 2.6°) about 58 min after the rocket launch strongly suggests that they were induced by the rocket launch. The characteristics of these DMLPDs identified from the in situ plasma measurements are (1) enhancement in electron temperature, (2) reduction in electron pressure, and (3) absence of electron density substructures.