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The usual way of displaying VLF Doppler experiment
data is by plotting a graph of group delay (ms) against time (UT), with the
signal intensity of the whistler-mode signals represented by a colour scale
as shown in the figure. The group delay scale is usually 0-970 ms, while the
time axis is typically about 24 hours long and has a time resolution of 15
minutes. At this stage there has been no attempt to remove the nonlinear
response of the experiment and the colour indicates the magnitude of
correlation coefficients between the whistler mode signal and the
sub-ionospheric signal. Distinct peaks in the correlation coefficients are
interpreted as representing field-aligned paths of plasmaspheric propagation
(ducts) and these can be seen to change in group delay over periods of
several hours. Similar plots can be used to study whistler-mode doppler
shifts and arrival bearings, each represented by the colour scale. |
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