Abstract
Abstract. We studied the temporal evolution of fractality for geomagnetic activity, by calculating fractal dimensions from the Dst data and from a magnetohydrodynamic shell model for turbulent magnetized plasma, which may be a useful model to study geomagnetic activity under solar wind forcing. We show that the shell model is able to reproduce the relationship between the fractal dimension and the occurrence of dissipative events, but only in a certain region of viscosity and resistivity values. We also present preliminary results of the application of these ideas to the study of the magnetic field time series in the solar wind during magnetic clouds, which suggest that it is possible, by means of the fractal dimension, to characterize the complexity of the magnetic cloud structure.
Highlights
There is a nontrivial magnetic interaction between Sun and Earth, coupled by the solar wind, leading to a rich variety of phenomena, which has attracted interest to the study of space plasmas for decades, and more recently to the possibility of forecasting space weather, an issue of large relevance in our increasingly technology-dependent society.Various models and techniques have been developed to study the plasma behavior in the Sun–Earth system
In this paper we review our results in this field, where complexity in magnetic field time series is measured by means of the fractal dimension
This does not hold for arbitrarily large values of j. We only find it for j > 1, but for values that are not too large, suggesting that it is within this range of values of j where the box-counting fractal dimension has statistical information on the dissipative events in the time series
Summary
There is a nontrivial magnetic interaction between Sun and Earth, coupled by the solar wind, leading to a rich variety of phenomena, which has attracted interest to the study of space plasmas for decades, and more recently to the possibility of forecasting space weather, an issue of large relevance in our increasingly technology-dependent society. In a previous work (Domínguez et al, 2017), we have applied the box-counting fractal dimension to study the complexity in an MHD shell model, analyzing the correlation between it and the energy dissipation rate, showing that, for certain values of the viscosity and the magnetic diffusivity, the fractal dimension exhibits correlation with the occurrence of bursts, similar to what had been found with geomagnetic data (Domínguez et al, 2014) This suggests that shell models do reproduce the power-law statistics of dissipative events in turbulent plasmas and some features of its fractal behavior. We present preliminary results dealing with spacecraft data for the solar wind, related to the appearance of magnetic clouds (Sect. 5)
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