Supergranulation is a particular pattern of convection cells on the Sun's surface called supergranules. It was discovered in the 1950s by A.B.Hart using Doppler velocity measurements showing horizontal flows on the photosphere (flow speed about 300 to 500 m/s, a tenth of that in the smaller granules). Later work (1960s) by Leighton, Noyes and Simon established a typical size of about 30000 km for supergranules with a lifetime of about 24 hours.
Supergranulation has long been interpreted as a specific convection tributaries. It should however be stressed that this picture is highly speculative and might turn out to be false in the light of future discoveries. Recent studies show some evidence that mesogranulation was a ghost feature caused by averaging procedures.
- Freedman, Roger A.; Kaufmann III, William J. (2008). Universe. New York, USA: W. H. Freeman and Company. p. 762.
- a SOHO/MDI Dopplergram showing supergranular speed pattern
- NASA: The Sun Does The Wave
- Information at Nature.com
- Michel Rieutord and François Rincon, "The Sun’s Supergranulation", Living Rev. Solar Phys. 7, (2010), 2. online article (cited on June 15, 2010).