Satellite observations of energetic electron precipitation effect on the polar vortex

Wintertime stratosphere and mesosphere are dominated by the polar vortex, a strong westerly wind system surrounding the pole. Polar vortex is variable and can even temporarily collapse during the winter, especially in the northern hemisphere. Several studies have shown that energetic electron precipitation (EEP) strengthens the northern polar vortex. Precipitating electrons come from the near-Earth space, the magnetosphere, and precipitate to the high-latitude thermosphere and mesosphere. There EEP forms odd nitrogen and hydrogen oxides (NO_X and HO_X) which destroy ozone and affect the temperature in the middle atmosphere. Most studies of the EEP effect on polar vortex have used reanalysis datasets which are based  on both observations and models. However, most reanalysis datasets are limited to stratospheric heights. We study here the EEP effect on the polar vortex and the modulation of this effect by planetary waves in the stratosphere and mesosphere with satellite measurements of EEP (POES/MEPED) and atmospheric properties (Aura/MLS). We derive the Eliassen-Palm flux, a measure for planetary wave activity, and the zonal wind from geopotential height observations. We show that EEP strengthens the stratospheric polar vortex, as found in earlier studies based on reanalysis data, but weakens the mesospheric polar vortex in the northern hemisphere. We also show that the EEP effect on polar vortex depends on the latitudinal distribution of planetary waves in the stratosphere and mesosphere.