Solar proton events of October–November 2003: Ozone depletion in the Northern Hemisphere polar winter as seen by GOMOS/Envisat

Observations of O 3 and NO 2 made by the GOMOS instrument on board European Space Agency's Envisat satellite have been used to monitor the increase of NO 2 and depletion of ozone due to the solar proton events of October–November 2003. For the first time this phenomenon was measured in polar winter conditions by a satellite instrument. Results show NO 2 enhancement of several hundred per cent and tens of per cent ozone depletion between 36 and 60 km, an effect which lasts several months after the events. A comparison of the after‐event concentrations of NO 2 and ozone reveals a strong negative correlation.