Daytime Midlatitude Plasma Depletions Triggered by the Launch of a Falcon 9 Rocket on 7 September 2017

A SpaceX Falcon 9 rocket was successfully launched from Kennedy Space Center in Florida at 14:00 UT on 7 September 2017. Shortly after this rocket launch (~88 min later), abnormal daytime midlatitude plasma depletions (DMLPDs) were observed at 15:28 UT over the east coast of the United States by the lower pair of the ESA's Swarm satellites. We found that the presence of those DMLPDs cannot be related to natural phenomena, such as the 7-8 September 2017 geomagnetic storm, the Hurricane Irma, and the X1.3 solar flare event which occurred on that day. The DMLPDs rarely occur because during daytime plasma depletions will be refilled by the photoionization of atmospheric gases. The presence of those DMLPDs (at 28-39°N GLAT, -75.5°E GLON) near Kennedy Space Center (~3.7° separation in geographic longitude) forcefully indicates that they were triggered by the launch of Falcon 9 rocket. Moreover, the features of the DMLPDs detected on 7 September 2017 are similar to those of the DMLPDs presented from the Swarm 2 Hz Level 1b data provided by Swarm A and C satellites after the launch of a Falcon 9 rocket at 18:51 UT on 24 August 2017. The features of those rocket-triggered DMLPDs are increase of electron temperature, decrease of electron energy density, and smooth electron density distribution (i.e., absence of substructures with scale size greater than 1 km).