Indices of Global Geomagnetic Activity
This service contributes to the
International Service of Geomagnetic Indices (ISGI) of the
Geomagnetic Kp Index
The planetary three-hour-range Kp index was introduced by J. Bartels in 1949 and is derived from the standardized K index (Ks) of 13 magnetic observatories. It is designed to measure solar particle radiation by its magnetic effects.
The Kp numbers of the previous month are available in tabular format
The most popular representation of the Kp indices is in form of the Bartels musical diagram ("musical scales").
most recent calculation and four complete solar rotations GIF or PS
most recent calculation and values since January 1 GIF or PS
There are available also historical and current Kp and derived indices per anonoymos FTP (see below).
Geomagnetic ap, Ap, Cp and C9
The geomagnetic ap, Ap,
Cp and C9 indices and the classification of
international Q-days and D-days are
derived from the Kp index.
- J. Bartels, The technique of scaling indices K
and Q of geomagnetic activity,
Ann. Intern. Geophys. Year 4, 215-226, 1957;
- J. Bartels,The geomagnetic measures for the time-variations of
solar corpuscular radiation, described for use in correlation
studies in other geophysical fields,
Ann. Intern. Geophys. Year 4, 227-236, 1957;
- M. Siebert, Maßzahlen der erdmagnetischen Aktivität,
in Handbuch der Physik,
vol. 49/3, 206-275, Springer, Berlin Heidelberg, 1971;
for the description of several indices (in German);
- M. Siebert and J. Meyer,
Geomagnetic Activity Indices,
in The Upper Atmosphere (Eds. W. Dieminger et al.),
887-911, Springer, Berlin Heidelberg, 1996;
for an updated version of the German reference;
- P.N. Mayaud,
Derivation, Meaning and Use of Geomagnetic Indices,
Geophysical Monograph 22,
Am. Geophys. Union, Washington D.C., 1980;
for a complete review of the present IAGA indices;
- G.K. Rangarajan,
Indices of magnetic activity,
in Geomagnetism, edited by I.A. Jacobs,
Academic, San Diego, 1989;
- M. Menvielle and A. Berthelier,
The K-derived planetary indices:
description and availability,
Rev. Geophys. 29, 3, 415-432, 1991.
Sources of Kp and derived indices
Beginning January 1997:
Adolf-Schmidt-Observatorium für Geomagnetismus
Ending January 1997:
Institut für Geophysik
World Data Center C1 for Geomagnetism
- E-mail distribution ended January 1997
- FTP server (daily mirror of Potsdam FTP server)
Danish Meteorological Institute
DK-2100 Copenhagen OE
World Data Center A for Solar-Terrestrial Physics
Boulder, CO 80303-3328
National Space Science Data Center
7701 Greenbelt Rd.
Greenbelt, MD 20770
IAGA Bulletin No. 32 (yearly compilation, irregular publication date)
As a member of the International Service of Geomagnetic
Indices, the GFZ, Adolf-Schmidt-Observatory Niemegk,
supplies historical and current Kp and derived indices per
anonymous FTP. Two FTP servers with identical structure are available:
Note: FTP sites may refuse connections due to excessive traffic.
- Denmark: ftp://ftp.dmi.min.dk/pub/Data/WDCC1/indices/kp-ap/
- Germany: ftp://ftp.gfz-potsdam.de/pub/home/obs/kp-ap/
Your mileage may vary with a different FTP program.
The kp-ap/ directory contains
readme.txt (text file)
- A plain text copy of the Geomagnetic Indices WWW page.
music.exe (binary executable file)
- A PC executable program for 386 or higher
machines. music.exe reads Kp/ap
values in WDC format and produces a PostScript file with Bartels
Kp music diagram. Download music.exe using
binary mode! The data file ssc.dat is also required
to run music.exe.
ssc.dat (text data file)
- List of sudden commencements (ssc),
- contains the monthly Kp/ap tables in a simple
text format readable for both humans and computers
(*.tab). The file
tab_fmt.doc provides a
The tables distributed by regular mail (PostScript format) are
also provided in this directory.
- contains the monthly (respectively yearly) Kp/ap
tables and much more information in condensed tables (ASCII
format). The format is nearly identical to the format of
Kp/ap tables distributed by the
World Data Center A for Solar-Terrestrial Physics. The file
wdc_fmt.doc provides a
This format does not contain any information on the quiet and
most disturbed days as the tables in the tab directory do.
- contains the Kp values in the Bartels musical diagram
(PostScript format), which is very helpful in visualizing the indices.
- contains tables of the quietest and most disturbed days for all
months since Jan 1932.
(Values since 1900 also supplied, use with caution.)
- contains tables of frequencies of Kp indices.
ap_monyr.ave (text file)
- A table with monthly and yearly averages of Ap.
For questions concerning specific data or the contents of this page,
Dr. H. -J. Linthe,
Last modified: Jul 17 2001