MDI observations of supergranulation
Date: 05 January 2003
Supergranules are large convection cells, measuring around 30 000 kilometres across (about two Earths across) but their origin and depth are currently unknown.
The thousands of supergranules that cover the Sun's surface are most easily visible in 'dopplergrams'. A dopplergram of the Sun, taken by the MDI instrument onboard SOHO, reveals motions on the Sun's surface with areas moving toward us appearing dark, and areas moving away, bright.
The smooth area near the center of the solar disk is where the supergranules do not contribute to the signal: their motion is mostly horizontal and MDI measures only the component of motion directed towards or away from SOHO. Supergranules flow outwards from their centers, with a typical velocity of 400 ms-1.
Copyright: SOHO/MDI (ESA/NASA)
Last Update: 1 September 2019