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A conjugate area study of Pc 3 pulsations near cusp latitudes

1990; American Geophysical Union; Volume: 95; Issue: A7 Linguagem: Inglês

10.1029/ja095ia07p10695

2156-2202

A. Wolfe, D. Venkatesan, R. Slawinski, C. G. Maclennan,

Geophysics and Gravity Measurements

Pc 3 pulsations are examined from conjugate studies at Iqaluit (Frobisher Bay), Northwest Territories, Canada, and at the geographic south pole, Antarctica ( L ∼ 14). These Pc 3 ( f ∼ 20–50 mHz) events are quantitatively selected from hourly power spectra of the H component magnetometer time series for local daytime hours. Above a cutoff frequency of 29 mHz we find that the frequency of these events has a linear relationship with hourly averages of the interplanetary magnetic field (IMF) magnitude as measured by the IMP 8 spacecraft while in the upstream region. These events are narrow‐banded and occur mostly in local morning and for IMF conditions with B x > 0, B y < 0, and B z > 0. Further, the frequency of the selected events is found to be independent of the IMF below the 29‐mHz cutoff. These characteristics of Pc 3 agree well with our previously reported Pc 3 events observed at South Pole (Slawinski et al., 1988). However, few simultaneous events are observed at Iqaluit and South Pole, indicating a lack of conjugacy on an event by event basis. We conclude that upstream ion cyclotron waves are a source of these Pc 3 events above 29‐mHz frequencies in both hemispheres. We speculate that the lack of conjugacy may be due to the station(s) being on open field lines during these events or that field line resonance may not be excited at Pc 3 frequencies for such high latitudes.