ROMA (Rank-Ordered Multifractal Analysis) Spectra for Intermittent Fluctuations with Nonlinear Crossover Behavior --- Electric Field in the Auroral Zone

ROMA (Rank-Ordered Multifractal Analysis) has the capabilities of deciphering the multifractal characteristics of intermittent fluctuations. The method allows one to understand the multifractal properties through global scale invariants. The utilities of ROMA, which combines the ideas of parametric rank ordering and single- parameter scaling of monofractals, were first demonstrated in its application to the results obtained from large-scale 2-D MHD simulations. In this study, we apply ROMA to the electric field fluctuations measured by the SIERRA sounding rocket in the auroral zone. The intermittent fluctuations span across time scales of multiple regimes that presumably reflect a change in the dominant physical processes. We extend the ROMA technique to take into account such nonlinear crossover behavior in the time scales, and obtain global scale invariants associated with the cross-regime multifractal spectra.