Alternate Definitions for region number

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Term: region number
Definition:

A number assigned by NOAA to a plage region or sunspot group if one of the following conditions exists: (1) the region is a group of at least sunspot classification C; (2) two or more separate optical reports confirm the presence of smaller spots; (3) the region produces a solar flare; (4) the region is clearly evident in H-alpha and exceeds 5 heliographic degrees in either latitude or longitude. (See also active region.)

Created 2023.04.16
Last Modified 2023.04.16
Contributed by Ryan McGranaghan
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