This is a chart that maps the monthly average of Sunspots total

Click HERE to compare the average Sunspot Numbers (S.I.D.C.) to the Cycle 24 predictions.

Complete History of Monthly Averages from 1991 to Current can be found at http://www.swpc.noaa.gov/ftpdir/weekly/RecentIndices.txt

The data below shows Sunspot numbers as recorded by SWO and not by the SIDC.

Month
High
Low
Sept 08
18
0
Aug 08
0
0
July 08
12
0
June 08
14
0
May 08
34
0
Apr 08
25
0
Mar 08
63
0
Feb 08
19
0
Jan 08
26
0
Dec 07
44
0
Nov 07
15
0
Oct 07
15
0
Sept 07
26
0
August 07
25
0
July 07
44
0
June 07
63
0
May 07
56
0
April 07
38
0
March 07
27
0
Feb 07
36
0
Jan 07
52
11
Dec 06
59
0
Nov 06
62
0
Oct 06
50
0
Sept 06
53
0
August 06
48
0
July 06
40
0
June 06
67
0
May 06
78
0
April 06
105
14
March 06
49
0

What is a sunspot ?

A sunspot is a region on the Sun's surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. Although they are blindingly bright, at temperatures of roughly 5000 K, the contrast with the surrounding material at some 6000 K leaves them clearly visible as dark spots. Interestingly, if they were isolated from the surrounding photosphere they would be brighter than an electric arc.

Sunspot Number Definition

This term is basically self-explanatory. It represents the number of observed sunspots and sunspot groups on the solar surface. It is computed according to the Wolf Sunspot Number formula: R = k (10g + s), where 'g' is the number of sunspot groups (regions), s is the total number of individual spots in all the groups, and k is a scaling factor that corrects for seeing conditions at various observatories.

Sunspot number varies in phase with the solar flux. Sunspot numbers can vary between zero (for sunspot minimum periods) to values in excess of 350 or 400 (in the very active "solar max" period of the suns 11 year cycle). Solar flux is related to the sunspot number, since sunspots produce radio emissions at 10.7 cm wavelengths (as well as at other wavelengths).

Different type of sunspot numbers

There is primarily two types of Sunspot Numbers used. One is the international sunspot number (RI) as reported by the Solar Influences Data Analysis Center (S.I.D.C) in Brussels, Belgium. The other is by Space Weather Operations (SWO) a division of the Spaceweather Prediction Center at NOAA. The international number is always higher than the SWO number. This is due to the observing techniques and calculations used. The S.I.D.C. have been using the same observation methods dating back to the 18th century. The SWO numbers are based on the USAF observatories which use relatively new telescopes. No adjustments are made to this Sunspot Number calculation.