The frequency characteristics and the waveforms of tweeks are analyzed theoretically. In the waveform analysis the mode current method is used: a method based upon the source current expansion and the multi-reflection. In the theory the source current is Fourier-expanded by using the electric images. The calculated frequency dispersion and the first mode waveform are compared with the observed ones and discussions follow.

The waveform of tweek atmospherics was analyzed theoretically. In the theory of mode currents the following two methods were used; the cylindrical wave method and multi-refrection method. In both methods the source current was Fourier-expanded by using the electric images. The identical frequency dispersion equation was then derived by the two methods. The calculated result was compared with the observed ones. In order to improve the theory. a source current waveform and the ray theory were introduced. The calculated first mode waveform was compared with the observed waveform and discussions followed.

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