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to the GDSO

DEFINITIONS OF SUNSPOT INDICES

The following are sunspot indices that the GDSO employs,
and states in its monthly and annual reports.

WOLF NUMBER [RELATIVE (SUNSPOT) NUMBER]

The Wolf Number is the most well known sunspot index. It has been used for
many years and international data in this series stretch back to 1749.
It is for this reason that the Wolf Number is in use today.
It is NOT a total of sunspots, but is defined as follows;

R = k(10g + f ) ,

where g = number of sunspot regions,
f = number of sunspots, and
k = local co-efficient to bring local observations to a world ‘standard’.

The value of k is obtained from dividing individual ‘international’ results by individual local results and calculating a mean for the period concerned.

ACTIVE AREA

The AA or g index is merely g in the Wolf Number above. Each region is
given 1 point. AA international results are calculated by the BAA Solar Section.

PETTIS INDEX

The Pettis Index (or Pettisindex) [SN or PX] is another sunspot index, but
it effectively gives more points to complex regions and fewer to small regions, than what the Wolf Number does. The definition is as follows;

SN = 10p + s ,

where p = number of penumbræ,
s = number of non-penumbral spots.
Umbræ within penumbræ are not counted.

BECK INDEX

The Beck Index (BX) was devised by Rainer Beck of Germany, and is calculated in the following manner;

          g

BX =  S Zifi ,

         i=1

where g = number of regions,
f = number of sunspots,
Z = region constant based on Zürich classes (A to H plus J), the
constants for the following regions are;

 A

 B

 C

 D

 E

 F

 G

 H

 J

 4

 4

 8

18

 25

 36

 50

 44

 37

 

CLASSIFICATION VALUE

The Classification Value system was devised by Kjell Inge Malde of Norway. It is calculated from the McIntosh classification system which is an extention of the Zürich classification
system, and is as follows;

           g

CV =  S Mi,

          i=1

where g = number of regions, and
M = region constant based on the McIntosh classes, which follow;

 AXX = 1

 DKI = 46

 ESO = 26

 BXI = 3

 DKO = 43

 FAC = 33

 BXO = 2

 DRI = 16

 FAI = 24

 CAI = 9

 DRO = 13

 FAO = 21

 CAO = 8

 DSC = 34

 FHC = 60

 CHI = 42

 DSI = 28

 FHI = 54

 CHO = 41

 DSO = 25

 FHO = 51

 CKI = 39

 EAC = 32

 FKC = 57

 CKO = 38

 EAI = 23

 FKI = 48

 CRI = 6

 EAO = 20

 FKO = 45

 CRO = 5

 EHC = 59

 FRI = 18

 CSI = 12

 EHI = 53

 FRO = 15

 CSO = 11

 EHO = 50

 FSC = 36

 DAC = 31

 EKC = 56

 FSI = 30

 DAI = 22

 EKI = 47

 FSO = 27

 DAO = 19

 EKO = 44

 HAX = 7

 DHC = 58

 ERI = 17

 HHX = 40

 DHI = 52

 ERO = 14

 HKX = 37

 DHO = 49

 ESC = 35

 HRX = 4

 DKC = 55

 ESI = 29

 HSX = 10

 

QUALITY COUNT & SQUARED QUALITY COUNT

The Quality Count was devised by Tony Tanti of Marsaxlokk, Malta GC. It gives a number to all 9 Zürich classifications, and is as follows;

           g

QC =  S Zi ,

          i=1

where g = number of regions, and
Z = region constant based on Zürich classes (A to H plus J), the
constants for the following regions are;

 

A

B

C

D

E

F

G

H

 

1

 2

3

4

5

6

4

3

2

Squared

1

4

9

16

25

36

16

9

4

 

INTER-SOL INDEX

The Inter-Sol Index was devised by the staff at the Paderborn Public Observatory, Germany, and is as follows;

IS = gr + grfp + grf +efp + ef

where gr = number of multi-spot regions,
grfp = number of sunspots within penumbræ within the groups (gr),
grf = number of sunspots free of penumbræ within the groups (gr),
efp = number of penumbral single sunspots,
and ef = number of penumbra-free single sunspots.

 

The GDSO applies a local co-efficient to all of its observed results, in the same manner as the k in the Wolf Number formula.

 

For a PDF version of the above, click here.

-oOo-