The auroral Q index is used in a wide range of models for the high-latitude ionosphere. This index was originally derived from analysis of auroral observations at high latitudes, originally from a collection of stations, but by the 1960s the index was calculated from a single station, Sodankyla, Finland. During the late 1960s and early 1970s a number of ionosphere models used by the USAF Air Weather Service required this parameter as an input, used to specify the location of several high-latitude ionospheric features. This index was not available in real-time, so a series of proxy, or effective, indices were developed, all denoted Qe.
The earliest Qe indices were derived from another proxy index, a real-time estimate of the geomagnetic Kp index. Later, algorithms were developed to estimate both Kp and Qe from visual observations of the auroral from the USAF Defence Meteorological Satellite Program (DMSP) satellite, and then from the SSJ precipitating electron sensor which measured the precipitating electrons which caused the aurora. There are, literally, a plethora of algorithms relating Qe, Kp, and the auroral precipitation (and emission) boundary, many of them functions also of the local magnetic time. The algorithm we have selected to use is from the following report which describes how it was developed as well as discussions of the history of these indices:
Dandekar, B. S. (1993), Determination of the Auroral Oval Q Index from the Air Weather Service K Index, PL-TR-93-2267, Phillips Laboratory, Hanscom AFB, MA, 18 Oct 1993 (AD-A282764).
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