region number

Alternative definitions (0), class: vernacular (0)
Term: region number

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