********************************************************************** thm_crib_twavpol.pro : with twavpol.pro ********************************************************************** This version stores these outputs as tplot variables with the specified prefix These are follows: Wave power: On a linear scale, at this stage no units Degree of Polarisation: This is similar to a measure of coherency between the input signals, however unlike coherency it is invariant under coordinate transformation and can detect pure state waves which may exist in one channel only.100% indicates a pure state wave. Less than 70% indicates noise. For more information see J. C. Samson and J. V. Olson 'Some comments on the description of the polarization states of waves' Geophys. J. R. Astr. Soc. (1980) v61 115-130 Wavenormal Angle: the angle between the direction of minimum variance calculated from the complex off diagonal elements of the spectral matrix and the Z direction of the input ac field data. For magnetic field data in field aligned coordinates this is the wavenormal angle assuming a plane wave. Ellipticity:The ratio (minor axis)/(major axis) of the ellipse transcribed by the field variations of the components transverse to the Z direction. The sign indicates the direction of rotation of the field vector in the plane. Negative signs refer to left-handed rotation about the Z direction. In the field aligned coordinate system these signs refer to plasma waves of left and right handed polarisation. Helicity:Similar to Ellipticity except defined in terms of the direction of minimum variance instead of Z. Stricltly the Helicity is defined in terms of the wavenormal direction or k. However since from single point observations the sense of k cannot be determined, helicity here is simply the ratio of the minor to major axis transverse to the minimum variance direction without sign. Written by : Kaori(I'll remember to get her last name soon) $LastChangedBy: pcruce $ $LastChangedDate: 2007-12-06 14:56:54 -0800 (Thu, 06 Dec 2007) $ $LastChangedRevision: 2161 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/ssl_general/trunk/misc/tplotxy.pro $