Observations of the effects of DPY currents at sub-auroral latitudes
Magnetograms from Lerwick, Scotland and Halley, Antarctica are used to show that the effects of the DPY current system can frequently be detected at these sub-auroral observatories. It is found that the magnetic perturbations associated with the DPY current dominate any effects that may be caused by the dawn-dusk displacement of the DP2 current resulting from the imposition of the y-component of the interplanetary magnetic field, By. The magnitude of the DPY current effect appears to be directly related to that of By, which is contrary to results from stations within the polar cap. There is no apparent seasonal variation in the frequency with which DPY effects are seen at Halley and Lerwick.