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Table 1

Bands of range values used to generate quantized K-indices for a station with a lower limit of the K = 9 band of L. ΔH X or Y is the range between extreme values in the 3-hour intervals of the northward or westward horizontal component, whichever is the larger. The right hand column gives the quantized aK values ascribed to the K-levels using the “K2aK” or “mid-class amplitudes” scale.

K value Range band aK (nT)
0 0 ≤ ΔH X or Y  < 0.01L 2.3
1 0.01L ≤ ΔH X or Y  < 0.02L 7.3
2 0.02L ≤ ΔH X or Y  < 0.04L 15
3 0.04L ≤ ΔH X or Y  < 0.08L 30
4 0.08L ≤ ΔH X or Y  < 0.14L 55
5 0.14L ≤ ΔH X or Y  < 0.24L 95
6 0.24L ≤ ΔH X or Y  < 0.40L 160
7 0.40L ≤ ΔH X or Y  < 0.66L 265
8 0.66L ≤ ΔH X or Y  < L 415
9 ΔH X or Y  ≥ L 667

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