On the Difference Between Polarisation and Coherence
In the analysis of plane waves - for example in optics or magnetic studies - it is
of primary interest to determine the polarisation parameters of the signal from
its measured components. Several methods have been presented to deal with this
problem in both two- and three-dimensions (Fowler et aI., 1967; McPherron et
aI., 1972; Means, 1972; Samson, 1973; Kodera et aI., 1977) but in this letter the
remarks are restricted to the two-dimensional case - they are equally valid
however in three-dimensions. It should be noted that many workers have
applied the techniques of these authors to analyse their own data (for example
Paulson, 1968; Rankin and Reddy, 1972; Arthur et aI., 1976; Jones, 1977;
Kodera et aI., 1977; Samson, 1977) and have shown the superiority of these
forms of frequency domain analyses to the time domain hodogram.
However, it has occurred to the author that there is not a widespread
appreciation of the (somewhat) subtle difference between the definitions of
polarisation and coherence. It is the purpose of this letter to show that the
distinction between polarised and unpolarised parts is not necessarily consistent
with that between coherent and incoherent parts.
Journal of Geophysics (Zeitschrift fuer Geophysik), 45, 223-229.
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Alan G Jones / 28 February 2010 /