Recent Observations of Rocket Exhaust Effects on the Ionosphere

In 1973, the launch of Skylab created a ~50% depletion in the daytime ionosphere over the N. Atlantic Ocean that lasted for hours. This effect was discovered in the data being routinely gathered by radio receivers monitoring the Total Electron Content (TEC) using the Faraday rotation of a signal from the ATS-3 geostationary satellite. This “ionospheric hole” was created by the H₂O and H₂ in the rocket exhaust reacting with the ambient O⁺ in the F region. This reaction is ~2 orders of magnitude faster than the “normal” reaction between O⁺ and the ambient O₂. Subsequent rocket launches were studied to confirm this process. Dedicated rocket launches were also used to create steep density gradients to study ionospheric instabilities near the magnetic equator. Today, rockets are being launched at an ever increasing rate (~2 launches/week), some of them causing ionospheric holes. The launches of Starlink group 6 from Florida de-orbit over the McDonald Observatory where Boston University has an All-sky Imager (ASI) dedicated to observing the optical emissions from the ionosphere. The de-orbit burns release H₂O and CO₂, both of which create an ionospheric hole with a concurrent burst of 630.0nm airglow. This airglow is bright enough (~ 10kR) to be seen with the unaided eye, and has been documented by citizen scientists. The resulting hole is also seen on GPS TEC maps of the region. Several examples of the de-orbit burns observed with the ASI at McDonald are shown.