Testing for multifractality of the slow solar wind

Abstract

Abstract We analyse a time series of the radial component of the Elsässer variable for the low-speed stream of the solar wind plasma representing Alfvénic fluctuations propagating downstream as measured in situ by the Helios spacecraft in the inner heliosphere. We demonstrate that the influence of noise in the data can be efficiently reduced by moving average and singular-value decomposition filters. We calculate the multifractal spectrum for the flow of the solar wind directly from the cleaned experimental signal. The resulting spectrum of dimensions shows a multifractal structure of the solar wind in the inner heliosphere. The obtained multifractal spectrum is consistent with that for the multifractal measure on the self-similar weighted Cantor set with the degree of multifractality of $10 À1