Active region numbers

[KevinOR]

This may seem a simple question - When were the active region numbers started? and who decided that in particular? are there references to this?

[Vancanneyt Sander]

A good question and I don't really know when they started giving out AR numbers... In our archive in 1996 we already where at AR7935 and now we're at AR12955 so in 26 years we have had 5020 active regions so with some simple math the counting should have started around 1955. But when I look at SWPC reports from 1966 they referenced "region 8240" for example but often they just referenced coördinates so there wasn't a systematic system yet.  So it's likely at some point in history the agencies worked together to unify the AR numbering but when, that's a good question...

[3gMike]

5 hours ago, KevinOR said:

This may seem a simple question - When were the active region numbers started? and who decided that in particular? are there references to this?

 

I found this quote on https://apod.nasa.gov/apod/ap020801.html

" While individual sunspots are not numbered or cataloged, groups of sunspots, designated solar active regions, are given consecutive numbers as they appear on the visible solar disk. That numbering began on January 5, 1972 and on June 14, 2002, reached active region number 10,000."

and this:

"The National Oceanic and Atmospheric Administration (NOAA) numbers active regions consecutively as they are observed on the Sun. According to David Speich at NOAA, an active region must be observed by two observatories before it is given a number (a region may be numbered before its presence is confirmed by another observatory if a flare is observed to occur in it, however). The present numbering system started on January 5, 1972, and has been consecutive since then."

from https://hesperia.gsfc.nasa.gov/sftheory/questions.htm#AR_numbers