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SUMMARY:Solar Effects on the Polar Atmosphere: The Role of Energetic Parti
 cle Precipitation - Dr Annika Seppälä\, BAS
DTSTART:20110214T141500Z
DTEND:20110214T151500Z
UID:TALK28111@talks.cam.ac.uk
CONTACT:Dr Alex Archibald
DESCRIPTION:This presentation I will give an overview of what has recently
  been learned about the impact of Solar energetic particle precipitation o
 n the polar stratosphere and mesosphere. I will discuss the further implic
 ations on troposphere via atmospheric coupling mechanisms and some of the 
 open questions on this linkage.\n\nA large solar disturbance such as a fla
 re or a coronal mass ejection results in emission of high-energy protons a
 nd other ions from the Sun. If these particles reach the Earth they set of
 f an event known as a Solar Proton Event. In addition to these events the 
 Earth continuously undergoes precipitation of energetic charged particles 
 (protons and electrons) originating from the near-earth space. The charged
  particles enter (i.e. precipitate into) the Earth's atmosphere causing io
 nisation in the middle atmosphere. This effect is confined to the polar re
 gions\, where the particles are guided by the Earth's magnetic field. In t
 he atmosphere the enhanced ionisation leads to increased production of odd
  nitrogen (NOx) and odd hydrogen (HOx) both of which participate in cataly
 tic reaction cycles decreasing the amount of ozone. HOx gases have a short
  chemical lifetime but the NOx gases are mainly destroyed by photodissocia
 tion. Hence during polar winter\, when little or no sunlight is present\, 
 the NOx impact on the atmosphere can be long-lasting. For example\, follow
 ing a series of large solar storms in Oct-Nov 2003\, a 60% ozone depletion
  in the Arctic upper stratosphere was observed a month after the storms. \
 n\nIn this talk I will show satellite based observations of the effects of
  solar storms and energetic particle precipitation on the chemical composi
 tion and dynamics of the polar middle atmosphere. In addition to observati
 ons\, I will also present modelling results from a detailed ion and neutra
 l chemistry model of the atmosphere. Recently\, analysis of meteorological
  data has indicated that during the winter season the distribution of pola
 r surface air temperatures shows variability depending on the level of NOx
  producing particle precipitation\, so finally\, I will discuss the long t
 erm effects of energetic particle precipitation on the atmosphere and the 
 possible further implications to polar climate via atmospheric coupling pr
 ocesses.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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