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Spherical harmonic analyses (order 4, degree 12) for the 1965 and 1958 geomagnetic Sq fields are compared, using similar displays, to determine the external and internal current changes from extremely quiet to extremely active solar cycle conditions. For the middle latitudes the active year currents were found to be about 1.6 to 3.0 times as large as the quiet year currents with the larger ratio occurring in mid‐November and the smaller ratio occurring near the June solstice. The maximum in daily Sq currents seemed to happen about 1/2 hour earlier in the quiet year results. The daily range of quiet year Sq variations showed a dominant annual change that was largest from late July to early August, whereas the active year daily range of Sq exhibited a dominant semiannual change with maxima at the equinoxes.
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Campbell et al. (1982) studied this question.
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