Granule (solar physics)

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Solar photosphere, with North America superimposed for scale. Each black or white bar on the graphic represents 1000 km.
Solar photosphere, with North America superimposed for scale. Each black or white bar on the graphic represents 1000 km.

Granules on the photosphere of the Sun are caused by convection currents of plasma within the Sun's convective zone. The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation.

The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. In addition to the visible appearance, Doppler shift measurements of the light from individual granules provides evidence for the convective nature of the granules.

The typical granule is in the order of 1000km and lasts 8 to 20 minutes before dissipating. Amid the typical granules are supergranules up to 30,000 kilometers in diameter with lifespans of up to 24 hours.

The Sun
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Image:Sun picture.png
Structure: Solar Core - Radiation Zone - Convection Zone
Atmosphere - Photosphere - Chromosphere - Transition region - Corona
Extended Structure: Termination Shock - Heliosphere - Heliopause - Heliosheath - Bow Shock
Solar Phenomena: Sunspots - Faculae - Granules - Supergranulation - Solar Wind - Spicules
Coronal loops - Solar Flares - Solar Prominences - Coronal Mass Ejections
Moreton Waves - Coronal Holes
Other: Solar System - Solar Variation - Solar Dynamo - Heliospheric Current Sheet - Solar Radiation - Solar Eclipse