Abstract
A chain of magnetometers has been placed in Antartica for comparisons
with magnetic field measurements taken in the northern hemisphere. The
locations were chosen to be on magnetic field lines that connect to
magnetometers on the western coast of Greenland, despite the difficulty
of reaching and working at such remote locations. We report on some
basic comparisons of the similarities and differences in the conjugate
measurements. Our results presented here confirm that the conjugate
sites do have very similar (symmetric) magnetic perturbations in a
handful of cases, as expected. Sign reversals are required for two
components in order to obtain this agreement, which is not commonly
known. More frequently, a strong Y component of the Interplanetary
Magnetic Field (IMF) breaks the symmetry, as well as the unequal
conductivities in the opposite hemispheres, as shown in two examples. In
one event the IMF Y component reversed signs twice within two hours,
while the magnetometer chains were approaching local noon. This switch
provided an opportunity to observe the effects at the conjugate
locations and to measure time lags. It was found that the magnetic
fields at the most poleward sites started to respond to the sudden IMF
reversals 18 min after the IMF reaches the bow shock, a measure of the
time it takes for the electromagnetic signal to travel to the
magnetopause, and then along magnetic field lines to the polar
ionospheres. An additional 9 to 14 min is required for the magnetic
perturbations to complete their transition.