Format Documentation of kpyymm.wdc Files


For the intermediate data transfer between the calculation and plot programs the Institut fuer Geophysik (Goettingen) has decided to use the standard format as published by the National Geophysical Data Center (NGDC) in Boulder, Colorado.


  • the columns for the solar radio flux (columns 66-71) are not fully maintained and might be missing
  • the list of most quiet and most disturbed days is not contained in this format; if you need those, please refer to the other tables (
  • the international sunspot number R might have provisional values in these tables, please refer to SIDC, Brussels, Belgium ( for R values

The following scientific and format documentation is adapted from:

Selected Geomagnetic and Solar Activity Indices

Worldwide Indices

The subscript p means planetary and designates a global magnetic activity index. The following 13 observatories, which lie between 46 and 63 degrees north and south geomagnetic latitude, now contribute to the planetary indices: Lerwick (UK), Eskdalemuir (UK), Hartland (UK), Ottawa (Canada), Fredericksburg (USA), Meanook (Canada), Sitka (USA), Eyrewell (New Zealand), Canberra (Australia), Lovo (Sweden), Brorfelde (Denmark), Wingst and Niemegk (Germany).

Three-hour-range Index Kp

Ks indices isolate solar particle effects on the earth's magnetic field; over a 3-hour period, they classify into disturbance levels the range of variation of the more unsettled horizontal field component. Each activity level relates almost logarithmically to its corresponding disturbance amplitude. Three-hour indices discriminate conservatively between true magnetic field perturbations and the quiet-day variations produced by ionospheric currents.

Ks indices range in 28 steps from 0 (quiet) to 9 (greatly disturbed) with fractional parts expressed in thirds of a unit. A Ks value equal to 27, for example, means 2 and 2/3 or 3-; a Ks value equal to 30 means 3 and 0/3 or 3 exactly; and a Ks value equal to 33 means 3 and 1/3 or 3+. The arithmetic mean of the Ks values scaled at the 13 observatories listed above gives Kp.

Equivalent Amplitude ap

The ap-index ranges from 0 to 400 and represents a Kp value converted to a linear scale in nT (nanoTesla) - a scale that measures equivalent disturbance amplitude of a station at which K=9 has a lower limit of 400nT.


Format Description


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