Effects of interplanetary magnetic sector structure on auroral zone and polar cap magnetic activity

Abstract

For quiet (C9 ≤ 2) and quiet to moderately disturbed (C9 ≤ 4) conditions in the period 1964-1968, the following sector structure dependence of auroral zone positive and negative bay activity, as measured by the AE components AU and AL, is noted. (1) There is a broad summertime peak in AU for both sector polarities, with AU higher for toward sectors during the first half of the year and with no apparent sector dependence during the second half of the year. (2) A stronger sector dependence is evident for AL, which peaks for toward sectors in the spring and for away sectors in the fall. (3) In a single 6-month period, negative bay magnitudes at College and at its southern hemisphere conjugate station, Macquarie Island, followed the same sector dependence as AL. (4) During this same period the ratio of College to Macquarie Island negative bay magnitudes was higher for away sectors than for toward sectors, and this asymmetry persisted through the midwinter crossover in sector dependence that occurred for each individual station. A similar N-S asymmetry is found in the polar cap. The ratio of DP 2 type activity at Vostok to that at Thule was greater by a factor of about 1.75 for toward sectors than for away sectors for periods near the 1967 spring and fall equinoxes.