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Fig. 2.


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Predicted and observed time-of-day/time-of-year patterns. The upper panel shows predictions based on geometric factors and the lower panel the contoured patterns in means of observations: (a) the Russell-McPherron (R-M) pattern; (b) the equinoctial pattern; and (c) the axial pattern (see text for details). In all plots red areas are maxima and blue are minima. (d) The R-M pattern is seen in the mean of the observed southward IMF in GSM coordinates, B S(GSM) (where B S(GSM) = −B Z(GSM) when B Z(GSM) < 0 and B S(GSM) = 0 when B Z(GSM) ≥ 0). (e) The equinoctial pattern is seen in the am geomagnetic index. (f) The axial pattern is seen in the corrected Dst index, −k(UT) × Dst, where the factor k(UT) is the modelled response of the 4 Dst stations that allows for the fact that they are not equally spaced in longitude. In all cases we are concerned only with the form of the pattern rather than the amplitude and colour scales have been auto-scaled between the maximum and minimum values.

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