The K index determined by the Air Force Global Weather Central has been compared with Kp and Q (from Sodankyla) for the period March 1978 - May 1981 to determine empirical relations between Kp vs K, Q vs Kp, and Q vs K. The study shows that the K index is a reasonably good measure of Kp during most of the time. The time-dependent relations between Q and K, and Kp and K are derived, so that one can convert the K (AFGWC) index to the Kp or Q index for specification of the auroral ionosphere in the Experimental Radar System test region.