or AR8090, was followed by AR8091.

According to the SWPC, a number is assigned to a region if it meets at least one of the following criteria:
# It contains a sunspot group of class C or larger based on the Modified Zurich Class sunspot classification system.
# It contains a sunspot group of class A or B confirmed by at least two observers, preferably with observations more than one hour apart.
# It has produced a solar flare with an X-ray burst.
# It contains plage with a white-light