Faculae and Sunspots at Solar Maximum and Solar Minimum

  • Released Tuesday, January 18, 2022
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The solar 'constant', the amount of energy received from the Sun during the course of the 11 year solar cycle, is not strictly constant. There is small variation during the course of the cycle due to the change in solar activity.

Sunspots form in regions with stronger magnetic fields on the photosphere and appear dark against the hotter solar surface, even though they are still quite hot. Faculae are extended regions that tend to form around sunspots and are hotter, and brighter, than the photosphere. Faculae are barely visible in solar imagery taken in visible light, but are more obvious in specific wavelengths (such as 1700 Angstroms used here) as the brighter speckled regions around many of the sunspots.

The hotter and more extended area of the faculae add more to the solar energy output than is taken away by the cooler and smaller sunspots, yielding a slight net increase in the solar luminosity around solar maximum.

Movie of SDO/HMI imagery, collected near solar maximum (April 2014). The small dark regions (sunspots) are readily visible, but the brighter faculae are generally only visible near the solar limb where 'limb darkening' provides sufficient constrast for them to stand out.


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This page was originally published on Tuesday, January 18, 2022.
This page was last updated on Wednesday, November 15, 2023 at 12:17 AM EST.


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