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Observations of turbulence and anomalous scaling in the solar wind

Abstract:

In situ observations collected in the past decades, at different heliocentric distances and covering almost the whole range of heliographic latitudes, represent a unique source of knowledge ready to be exploited to better understand the nature and the behavior of solar wind MHD turbulence. In fact, the solar wind can be used as an ideal wind tunnel in order to test turbulence models and investigate scaling laws and multifractal models within the framework of the theory of complex dynamical systems. Moreover, an important role is played by the presence of the large scale interplanetary magnetic field which introduces a preferential direction in the solar wind. This direction is particularly relevant not only for the propagation of the fluctuations and their anisotropy but also for the topology of the structures convected by the wind. As a matter of fact, recent results have shown that a complete picture of solar wind turbulence goes well beyond the role played by inward and outward stochastic Alfvénic fluctuations and takes into account also the presence of magnetically dominated coherent structures convected by the wind. This further ingbkp_redient of interplanetary turbulence can be either locally generated by turbulent dynamics or be the interplanetary signature of the complicated magnetic topology present at the basis of the corona. This paper aims to briefly review the present state-of-the-art in this field. © 2007 American Institute of Physics.