Baseline
Historically, baselines for a given day have been removed by manually identifying
a nearby quiet day and defining the measured
field as the quiet time field. Despite the merits of his method the data volume
for the SuperMAG collaboration invalidates this
method. An automated baseline determination technique has been developed (paper
in preparation) by SuperMAG PI Dr. Gjerloev.
The automated procedure removes the yearly trend as well as daily variation
(including contributions from the Sq current system).
The technique is not based on the classical quiet day definition but derives
the baselines from the data itself.