Other
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsa24a..04s&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SA24A-04
Other
0340 Middle Atmosphere: Composition And Chemistry, 0341 Middle Atmosphere: Constituent Transport And Chemistry (3334), 2716 Energetic Particles: Precipitating, 3360 Remote Sensing
Scientific paper
A large solar disturbance like a flare or a CME 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 the SPEs the Earth continuously undergoes precipitation of energetic charged particles originating from the near-earth space. The charged particles enter 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 and odd hydrogen, which take part in catalytic reaction cycles decreasing the amount of ozone. HOx gases have a short chemical lifetime while 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 O3 and NO2 observations in the polar middle atmosphere (30-70km) from the GOMOS stellar occultation instrument on board the Envisat satellite to study the effects of energetic particle precipitation on the stratosphere and mesosphere during 2002-2006. High amounts of NO2 are observed in 70% of the polar winter periods. Of the observed high NOx cases 80% are accompanied by increased geomagnetic activity and/or enhanced high-energy proton precipitation. For the remaining cases other production mechanisms are proposed. The ozone observations show that ozone loss takes place in the upper stratosphere following the observed NOx enhancements.
Backman Leif
Hassinen S.
Kyrola Erkki
Seppälä Annika
Sofieva V. F.
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