Magnetometer
A La Cour magnetometer was first deployed at Halley in 1957 as a contribution to the International Geophysical
Year, and a magnetometer has been operating there ever since. There are many difficulties associated with
making measurements on a moving ice-shelf, and especially in a regime where the magnetometer housing becomes
buried deep below the snow's surface (Simmons and Rouse, 1984). The position of the observatory is determined
from a satellite navigation system; the station is currently moving westwards at approximately 700 m per
year. As a consequence, no absolute measurements are made, and the station currently operates as a variometer
station utilising an EDA fluxgate magnetometer. The H, D and Z components of the Earth's magnetic field
are digitally sampled once every second with a resolution of ~1 nT.
The magnetometer data are used in support
of all geospace studies at Halley. In the past, they have been used only occasionally as the principal
data-set to investigate geospace processes, e.g. for determining the effects of the y-component of the interplanetary
magnetic field on the ionospheric current systems on the night-side (Rodger et al., 1984) and the dayside (
Rodger and Cowley, 1986). This limitation, imposed by the isolation of the instrument, has now been removed
with the introduction of a growing network of magnetometers on the multi-national array of AGOs. This network
will allow a wide variety of research of the type already demonstrated by the exploitation of data from
CANOPUS, SAMNET, MACCS, the EISCAT Cross, the Greenland chain and other magnetometer arrays, to be carried
out.
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