Abstract:We present a new approach for analyzing local power law processes and apply it to temperature measurements from the upper atmosphere. We segment the data and use the wavelet scale spectrum to estimate the parameters of the power law, the scale factor and the exponent. These parameters vary from segment to segment. Part of this variation is due to the non-stationarity of the data. Another part is due to estimation errors that depend on the segmentation. In this paper show h o w to remove e ectively these segmen… Show more
“…Important issues, relevant for interpretation of results, such as the choice of segmentation and filtering to smooth out the effects of segmentation, are described in detail in [22] and [25]. The intervals of stationarity are determined from a variogram (second order structure function) analysis of the wavelet coefficients.…”
Section: Partitioning Of Data Into Segments Of Equal Temporal Extentmentioning
confidence: 99%
“…The lower limit of the segment size is governed by the maximum temporal extent of the inertial range. No effects of partitioning on estimation of the inertial range or the turbulence parameters σ and H were detected due to the procedure for removal of segmentation dependent effects [22,25].…”
Section: Local Features Of Mast and Tore Supra Edge Turbulencementioning
A multifractal analysis based on evaluation and interpretation of large deviation spectra is applied to plasma edge turbulence data from different devices (MAST and Tore Supra). It is demonstrated that in spite of some universal features there are unique characteristics for each device as well as for different confinement regimes. In the second part of the exposition the issue of estimating the variable power law behavior of spectral densities is addressed. The analysis of this issue is performed using fractional Brownian motion (fBm) as the underlying stochastic model whose parameters are estimated locally in time by wavelet scale spectra. In this manner information about the inertial range as well as variability of the fBm parameters is obtained giving more information important for understanding edge turbulence and intermittency.
“…Important issues, relevant for interpretation of results, such as the choice of segmentation and filtering to smooth out the effects of segmentation, are described in detail in [22] and [25]. The intervals of stationarity are determined from a variogram (second order structure function) analysis of the wavelet coefficients.…”
Section: Partitioning Of Data Into Segments Of Equal Temporal Extentmentioning
confidence: 99%
“…The lower limit of the segment size is governed by the maximum temporal extent of the inertial range. No effects of partitioning on estimation of the inertial range or the turbulence parameters σ and H were detected due to the procedure for removal of segmentation dependent effects [22,25].…”
Section: Local Features Of Mast and Tore Supra Edge Turbulencementioning
A multifractal analysis based on evaluation and interpretation of large deviation spectra is applied to plasma edge turbulence data from different devices (MAST and Tore Supra). It is demonstrated that in spite of some universal features there are unique characteristics for each device as well as for different confinement regimes. In the second part of the exposition the issue of estimating the variable power law behavior of spectral densities is addressed. The analysis of this issue is performed using fractional Brownian motion (fBm) as the underlying stochastic model whose parameters are estimated locally in time by wavelet scale spectra. In this manner information about the inertial range as well as variability of the fBm parameters is obtained giving more information important for understanding edge turbulence and intermittency.
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