Multifractal behaviour of the ionospheric scintillation index time series over an Indian low latitude station Surat

• GPS based S4 index time series were used to study the fractal properties.
• Multifractal detrended fluctuation analysis method is used in analysis.
• Degree of multifractality and Hölder exponent were calculated.
• Scintillation occurrence were compared with multifractal spectra.
• Shape of spectrum was affected by small-scale intermittency of turbulent ionosphere.

The amplitude scintillation information recorded by the GSV4004B GISTM (Global Ionospheric Scintillation TEC Monitor) GPS receiver at an Indian low latitude station Surat (21.16°N, 72.78°E) for 48 months during the years 2009, 2010, 2011 and 2012 are utilized in the present work. Multifractal detrended fluctuation analysis (MF-DFA) have been carried out along with computation of q-order fluctuation function, q-order Hurst exponent, q-order mass exponent and multifractal spectrums for each monthly post-sunset S4 index time series. The non-linear dependence of mass exponent and dependence of q-order Hurst exponent on q-values reflect the existence of nonlinear interaction between different scales and multifractal structure in the system, respectively. The comparison of broadness and shape of spectra with the occurrence of scintillation activities registered in the same period reveal the existence of multifractality/complexity in the turbulent ionosphere, which is influenced by the small-scale intermittency and solar flux indices. The truncation of the spectrum is the evidence of manifestation of small-scale intermittency of the turbulent ionosphere. The higher values of the Hölder exponent α0, calculated from the spectrum, imply the irregular nature of the underlying process. The present study suggests that, MF-DFA may act as an important non-linear technique for identifying the effect of large and small-scale fluctuations in complex and turbulent ionosphere.