Indices of Global Geomagnetic Activity

This service contributes to the International Service of Geomagnetic Indices (ISGI) of the IAGA.

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 Indices

    The geomagnetic ap, Ap, Cp and C9 indices and the classification of international Q-days and D-days are derived from the Kp index.


    Sources of Kp and derived indices

  • Beginning January 1997:
  • GeoForschungsZentrum Potsdam
    Adolf-Schmidt-Observatorium für Geomagnetismus
    Lindenstraße 7
    D-14823 Niemegk
  • Ending January 1997:
    Institut für Geophysik
    Universität Göttingen
    Postfach 2341
    D-37013 Göttingen
  • World Data Center C1 for Geomagnetism
    Danish Meteorological Institute
    Lyngbyvej 100
    DK-2100 Copenhagen OE

  • World Data Center A for Solar-Terrestrial Physics
    325 Broadway
    Boulder, CO 80303-3328
  • National Space Science Data Center
    7701 Greenbelt Rd.
    Suite 400
    Greenbelt, MD 20770
  • IAGA Bulletin No. 32 (yearly compilation, irregular publication date)

    Structure of the FTP sites

    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.
    ;-) 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), partly preliminary.
    tab/ (subdirectory)
    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 format description. The tables distributed by regular mail (PostScript format) are also provided in this directory.
    wdc/ (subdirectory)
    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 format description. This format does not contain any information on the quiet and most disturbed days as the tables in the tab directory do.
    music/ (subdirectory)
    contains the Kp values in the Bartels musical diagram (PostScript format), which is very helpful in visualizing the indices.
    quietdst/ (subdirectory)
    contains tables of the quietest and most disturbed days for all months since Jan 1932. (Values since 1900 also supplied, use with caution.)
    kp-freq/ (subdirectory)
    contains tables of frequencies of Kp indices.
    ap_monyr.ave (text file)
    A table with monthly and yearly averages of Ap.

    Related WWW Servers

    For questions concerning specific data or the contents of this page, please contact:
    Dr. H. -J. Linthe,
    Last modified: Jul 17 2001