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Main Page   >   Данные   >   --> Geomagnetic Variations   >   Indices of geomagnetic activity   >   Kp, ap and Ap indices

Kp, ap and Ap Indices of Geomagnetic Activity

Кр index is a planetary index characterizing the global disturbance of the Earth's magnetic field in a three-hour time interval. The index Kp is defined as the average value of the disturbance levels of the two horizontal components of the geomagnetic field observed at 13 magnetic observatories located in the subauroral zone between 48 and 63 degrees of the north and south geomagnetic latitudes.
Kp index has 28 values in the range from 0 to 9 and is determined to within 1/3:
0о, 0+, 1-, 1о, 1+, 2-, … 8-, 8o, 8+, 9-, 9о.
The values of the Kp index are determined from 1932.

ар index is calculated from the values of Kp index and represents the variation of the most disturbed element of the magnetic field D or H in three-hour time interval at mid-latitude stations. ap index is called the planetary amplitude in the three-hour interval. ар index varies from 0 to 400 and represents the values of Kp converted to a linear scale in nT, which shows an equivalent amplitude disturbance at the station, which has a lower limit of 400 nT for K = 9.

Ар index is obtained by averaging eight values of ap per day and therefore is the equivalent daily average planetary amplitude of the earth's magnetic field perturbation with a linear scale. Ap index is defined in nanoscale in the range of values from 0 to 280 nT.

Index Kp and related indexes ap, Ap, Cp are determined in the Helmholtz-Centre Potsdam - GFZ German Research Centre for Geosciences, Potsdam, as a member of the International Service of Geomagnetic Indices.

Kp, ap and Ap index data from 1932 in WDC format.

Kp, ap and Ap index data from 1932 in IAGA2002 format

WDC for STP, Moscow is grateful to the ISGI Collaborating Institute GFZ German Research Centre for Geosciences, Potsdam, the INTERMAGNET network and International Service of Geomagnetic Indices – ISGI (

Using the data, please be sure to indicate the above organizations according to the following template.

How to Cite Datasets: Ball, A. and M. Duke [2011], How to cite datasets and link to publications, DCC How-to Guides, Edinburgh: Digital Curation Centre.

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