Cosmics Leaving Outdoor Droplets or the CLOUD is an experimental facility being set up at CERN by Jasper Kirkby to investigate the microphysics between Galactic cosmic rays (GCRs) and clouds under controlled conditions. The equipment is expected to become fully operational in 2011.[1]
There are two different hypotheses to link GCRs with clouds. The first is that the ionisation from GCRs increase the number of cloud condensation nuclei (CCN), upon which cloud droplets form. The second hypothesis is that GCR ionisation modulates the entire ionosphere-Earth electric current which, in turn, influences cloud properties through charge effects on droplet freezing.[1]
The experiment comprises a 4 m diameter aerosol chamber and a 0.5 m diameter cylindrical cloud chamber which are exposed to an adjustable particle beam which simulates GCRs at any altitude or latitude. The chambers are filled with air, water vapour and selected trace gases and aerosols and can be operated at any temperature or pressure found in the atmosphere. UV illumination allows photolytic reaction. Each chamber contains an electric field cage to control the drift of small ions and charged aerosols.[1]
CERN posted a 2008 progress report on the CLOUD project. [2] J. Kirkby (2009) reviews developments in the CERN CLOUD project and planned tests. He describes cloud nucleation mechanisms which appear energetically favorable and depend on GCRs.[3], [4]
References
- ^ a b c "CLOUD Proposal Documents". http://cloud.web.cern.ch/cloud/. Retrieved on 2008-10-20.
- ^ 2008 PROGRESS REPORT ON PS215/CLOUD Kirkby, Jasper, The CLOUD Collaboration, CERN, Geneva, SPS and PS Experiments Committee, SPSC, May 15, 2009
- ^ Cosmic Rays and Climate Video Jasper Kirkby, CERN Colloquium, 4 June 2009
- ^ Cosmic Rays and Climate Presentation Jasper Kirkby, CERN Colloquium, 4 June 2009
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