Modal Study of "Tweek"-Atmospherics

A new technique is used for analysis polarization parameters of experimental records of tweek-atmospherics (tweeks). Tweeks are observed during nighttime and represent a response of the Earth-ionosphere waveguide excited by lightning strokes. Tweeks are formed by series of pulses consecutively reflected from the waveguide boundaries under different incident angles depending on a source-observer distance and average effective ionosphere height along a propagation path. Using a source location technique described in our previous works we determined geometrical propagation path parameters such as source range, ionosphere height, and orientation of a propagation path in refer to magnetic meridian. We used then a time-frequency representation of the analyzed tweek waveforms to infer polarization parameters of the electromagnetic waves propagated under different incident angles as the first waveguide mode. Obtained dependencies of these polarization parameters show substantial difference depending on a propagation path length and its orientation