Indices of Global Geomagnetic Activity
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.
Musical Kp Diagram
The most popular representation of the Kp indices is in form
of the Bartels musical diagram
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.
Km is an index similar to Kp, except for the different
number and selection of stations and the method of averaging. The indices
am and Am are similar to ap and Ap.
Km, am and Am are evaluated at
l'Institut de Physique du Globe
in Paris, France.
- 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
Historical and current Kp are supplied by the
International Service of Geomagnetic Indices.
Calculation and distribution of the indices are now performed
by the GeoForschungsZentrum Potsdam. Two anonymous 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/
- ( WWW access: http://www.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,
Last modified: 29 Apr 1997