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Observations of Energetic Particle Effects on the Stratosphere

Annika Seppälä(1), Erkki Kyrölä(1), Pekka T. Verronen(1), Viktoria Sofieva(1), Johanna Tamminen(1), Seppo Hassinen(1) and Leif Backman(1)

(1) Finnish Meteorological Institute, Erik Palmenin aukio 1, FI-00101 Helsinki, Finland

Abstract

A large solar disturbance like a flare or a coronal mass ejection can result in emission of high-energy protons and other ions from the Sun. If these particles reach the Earth they set off an event known as a Solar Proton Event. In addition to these events the Earth continuously undergoes precipitation of energetic charged particles originating from the near-earth space. The charged particles precipitate into the Earth's atmosphere causing ionization in the middle atmosphere. The primary effect is confined to the polar cap regions, where the particles are guided by the magnetic field. In the atmosphere the enhanced ionization leads to increased production of odd nitrogen (NOx) and odd hydrogen (HOx) which participate in catalytic reaction cycles decreasing the amount of ozone. HOx gases have a short chemical lifetime but the NOx gases are mainly destroyed by photodissociation. Hence during polar winter, when little or no sunlight is available in the atmosphere, the effect of the NOx cycles can be long-lasting and extend outside the polar cap regions though transport processes in the atmosphere.

We have used ozone and NO2 observations from the GOMOS instrument on board the Envisat satellite to study the effects of energetic particle precipitation on the stratosphere. Both solar storm and non-solar-storm related energetic particle precipitation cases have been considered. GOMOS observations indicate that high energy particle forcing has a great impact on the stratospheric composition.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry