Region Designations

[Calder]

If a plage develops sunspots and becomes an active region, does it keep the same designation or does it get a new one? I always assumed it would keep the same designation, but I don’t really know.

[3gMike]

39 minutes ago, Calder said:

If a plage develops sunspots and becomes an active region, does it keep the same designation or does it get a new one? I always assumed it would keep the same designation, but I don’t really know.

If you look at the Synoptic map you will see that the plage is still designated 3267 and, in a slightly different location, we have the new spot AR3270

 

 

[Calder]

3 hours ago, 3gMike said:

If you look at the Synoptic map you will see that the plage is still designated 3267 and, in a slightly different location, we have the new spot AR3270

 

 

Thanks, but maybe I need to rephrase. I was already looking at the synoptic map for today, and noticed that they are separate regions. What I was asking was whether a plage/faculae region gets a new number if it develops sunspots? For example, if the plage region (3267) started to develop sunspots, would it become active region 3267?

[3gMike]

11 minutes ago, Calder said:

Thanks, but maybe I need to rephrase. I was already looking at the synoptic map for today, and noticed that they are separate regions. What I was asking was whether a plage/faculae region gets a new number if it develops sunspots? For example, if the plage region (3267) started to develop sunspots, would it become active region 3267?

Understood. I found this definition from SWPC

"Regions are assigned SWPC region numbers if one of the following conditions exists: (1) the region has a sunspot group with a first digit spot class of C, D, E, F or H (see figure 2), (2) two or more reports confirm the presence of class A or B spot group, (3) the region produces a solar flare, or (4) the region is “bright” in Hα and exceeds 5 heliographic degrees in either latitude or longitude."

They also say 

"Solar magnetic field measurements are used to assist in defining bipolar areas and to determine the approximate boundaries of each active area. It is not uncommon to have widely separated small spots within an extended bipolar region during an active region’s declining phase. This phenomenon occasionally leads to assignment of two or more different numbers to spots that actually originate within the same region."

That leads me to believe that usually if a plage region re-develops spots it would keep the same AR number.

If you want to learn more I suggest that you read the User Guide https://www.swpc.noaa.gov/sites/default/files/images/u2/Usr_guide.pdf

[Calder]

After reading that user guide and some other stuff, I think I’ll have to assume my assumption is correct. Plage regions must keep the same designation after developing/re-developing sunspots.