Magnetic Impulse Events at High Latitudes: Magnetopause and Boundary Layer Plasma Processes

Magnetic field data acquired at high latitude, near-conjugate stations (Iqaluit, Northwest Territories, Canada and South Pole Station, Antarctica) are studied in order to examine in more detail the nature of magnetic `impulse` signatures that occur in the data and that are produced by ionosphere currents which are caused by magnetopause processes. An examination of the data, both visually and with a computer algorithm `detector`, from the five month interval July-November 1985 found many such magnetic `impulse` events which could be interpreted in terms of intense field-aligned currents above the observing stations. All the events have a half-width in time of a few minutes and most are reasonably conjugate. The majority of the events studied have magnetic field perturbations in the vertical component which can be interpreted in terms of field-aligned currents directed in the same direction (either into or out of the ionosphere) in both hemispheres.