Processing magnetograms from stations of К р calculations in order to estimate the planetary index during strong magnetic disturbances

This paper deals with the study of preprocessing of magnetograms from stations of К р calculations in order to estimate the planetary index during strong geomagnetic disturbances. The modern technique for processing magnetograms does not allow us to take account of the dynamics of space-time variation in magnetosphere-ionosphere current systems, resulting from variation in the magnetic field topology during magnetospheric disturbances. Within this period, size and location of polar cap boundaries and auroral oval vary. We may encounter a situation in which the network of stations of К р calculations is partially in the polar region, and the index values estimated over these periods of time correspond rather to the local substorm activity than to the planetary geomagnetic one. This results in overestimated index values. Apart from inaccurate estimates, the present index allows a qualitative error, reflecting the state of current systems that are not related to middle latitudes (polar electrojets, particle precipitation in the cusp). The technique proposed for the preliminary correction of magnetograms allows us to eliminate an excessive influence of high-latitude foreign sources of magnetospheric disturbances upon estimated Кр values.