Algorithm of calculation of magnetic activity indexes

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In the report we consider the algorithm allowing to automate the calculation of magnetic activity indexes
in real-time, reproducing the J. Bartels’s method of calculation of K-indexes. The magnetic activity K-index,
introduced by J. Bartels in 1938, is a measure of maximum deviations during consecutive three-hour intervals
of geomagnetic field values from a quiet daily Sq-variation - the average smoothed curve, made by several
magnetograms of a quiet field with clearly defined day variations (usually five magnetograms per month are
used).
Now many observatories use different methods to find the quiet daily Sq-variation; they are based on
mathematical processing of magnetic field variations within every day, such as FMI-method. The advantage of
these methods is the immediacy, however, such geomagnetic activity indexes differ from Bartels’s K-indexes in
general.
This work presents the algorithm to calculate magnetic activity indexes; it is based on Bartels’s method, but
uses automatic calculation of a quiet daily Sq-variation. The days of quiet geomagnetic field are determined by
the previously calculated indexes. Thus, the introduced algorithm provides both tracing of Sq-variation changes
and calculation of magnetic activity indexes in real-time.
The calculations of magnetic activity indexes according to the data obtained at Borok Geophysical Observa-
tory [58.07N, 38.23E] for different modifications of the described algorithm and for different time intervals are
demonstrated. It is shown that the values of the calculated indexes adequately characterize geomagnetic field
disturbances and well agree with the values of K-indexes presented in the Internet by a number of geomagnetic
observatories.