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Fig. 3

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The variation of the scale factor s(δ) derived from threshold range value L that defines the K = 9 band, with the minimum angular separation of the station from a nominal auroral oval, δ. This empirical variation is scaled from Mayaud (1968, 1972) and is the basis of the L values used to scale K-indices from observed range for all mid-latitude stations. The scale factor s(δ) normalizes to the idealized Niemegk station for which δ = 19° and L = Lo = 500 nT (ideal static Mayaud values).

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