Resolution No.4 (1963): K-index

The IAGA recommends:

  1. that from the 1st of January, 1964, the Z-component will not be used for the measure of the three-hourly K-index, except by the standard Kp-observatories, and
  2. that for new observatories, the lower limit for K=9 should be chosen in consultation with the working group on magnetic activity indices of Commission No.4.