Abstract
The effect of energetic electron precipitation in the atmosphere has been an area of high interest in recent years. There are many different drivers pushing electrons into our atmosphere and while some are now accounted for in climate models, others are not. An important one that is yet to be included are substorms. Substorms occur in the magnetosphere and cause electrons to be lost into our atmosphere. The energies of these electrons allow them to precipitate to between 55 km and 95 km altitude. The electrons ionise neutrals in the atmosphere resulting in the production of HOx and NOx, which catalytically destroy ozone. The loss of ozone has previously been studied through simulations, however, this has not previously been verified from observations. This study primarily uses the Microwave Limb Sounder (MLS) instrument which measures gas constituents throughout the atmosphere including polar ozone. Analysis of observations from this instrument show a reduction of polar mesospheric ozone by up to 30% on average after a substorm onset. Substorms also have the ability to trigger ElectroMagnetic Ion Cyclotron (EMIC) waves which can cause higher energy electron precipitation, high enough to reach the stratosphere. To date, there are no studies investigating a stratospheric response to EMIC events. This is potentially the first piece of evidence pointing to stratospheric disturbance due to EMIC-triggered precipitation, as well as, the first observational evidence showing substorms are important to the ozone balance within the atmosphere and, hence, the climate.