**GEORGI DOBROVOLSKI SOLAR
OBSERVATORY**

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 ‘international’ results by local results.

**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 penumbrĉ,

s = number of non-penumbral spots.

Umbrĉ within penumbrĉ 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

Stavanger, 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__

The Quality Count was devised by Tony Tanti of Naxxar,
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 |
J |

1 |
2 |
3 |
4 |
5 |
6 |
4 |
3 |
2 |

__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 penumbrĉ within the groups (gr),

grf = number of sunspots free of penumbrĉ 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.