From AMS Glossary
A space weather term to describe a localized, transient volume of the solar atmosphere in which plage, sunspots, faculae, solar flares, etc., may be observed. Active regions are the result of enhanced magnetic fields; they can have bipolar or multi-polar magnetic fields, and can be ephemeral to long-lived in nature.
Wikipedia, The Free Encyclopedia, 2018: Euler angles. Accessed 9 April 2018. Wikipedia, https://en.wikipedia.org/wiki/Euler_angles.
Term edited 13 August 2018.