Wavelet analysis of ADITYA edge turbulence: Evidence of non-linear interaction

The edge turbulence in the ADITYA tokamak [Phys. Rev. Lett. 69, 1375 (1992)] is examined using wavelet analysis techniques. The wavelet filters are used to separate low and high frequency components. The filtered plasma density and floating potential fluctuations show leptokurtic non-Gaussianity (kurtosis, K approx-gt 3) at high frequencies, whereas, the low frequency components are nearly Gaussian. The recently developed wavelet bicoherence technique [Phys. Plasmas 2, 3017 (1995)] is extended to the Mexican hat wavelet. When the data are examined using wavelet bicoherence technique, it is found that the turbulent density and potential signals exhibit episodes of quadratic interaction in which low and high frequency components are coupled. copyright 1996 American Institute of Physics