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PCI Derivation and Representation

Copyright WDC C1 for STP at RAL.

It is derived from the horizontal magnetic perturbation in the central polar cap, measured at a single station located very near to the pole. The PC index is obtained by normalization with respect to the solar wind parameter, and a natural unit for PC would therefore be "equivalent" mV/m. It should be stressed, however, that PC is primarily an index of geomagnetic activity, and only in a statistical sense a measure of the electric field.