paper

Turbulent Reconnection and Its Implications

arXiv:1502.01396 · doi:10.1098/rsta.2014.0144

Abstract

Magnetic reconnection is a process of magnetic field topology change, which is one of the most fundamental processes in magnetized plasmas. In most astrophysical environments the Reynolds numbers are large and therefore the transition to turbulence is inevitable. This turbulence must be taken into account for any theory of magnetic reconnection, since the initially laminar configurations can transit to the turbulence state, what is demonstrated by 3D high resolution numerical simulations. We discuss ideas of how turbulence can modify reconnection with the focus on the Lazarian & Vishniac (1999) reconnection model and present numerical evidence supporting the model and demonstrate that it is closely connected to the concept of Richardson diffusion and compatible with the Lagrangian dynamics of magnetized fluids. We point out that the Generalized Ohm's Law, that accounts for turbulent motion, predicts the subdominance of the microphysical plasma effects for a realistically turbulent media. We show that on of the most dramatic consequences of turbulence is the violation of the generally accepted notion of magnetic flux freezing. This notion is a corner stone of most theories dealing with magnetized plasmas and therefore its change induces fundamental shifts in accepted paradigms like turbulent reconnection entailing the diffusion process that is essential for understanding star formation. We argue, that at sufficiently high Reynolds numbers the process of tearing reconnection should transfer to turbulent reconnection. We discuss flares predicted by turbulent reconnection and relate them to solar flares and gamma ray bursts. We analyze solar observations, measurements in the solar wind or heliospheric current sheet, and show their correspondence with turbulent reconnection predictions. Finally, we discuss 1st Order Fermi acceleration as a natural consequence of the turbulent reconnection.

48 pages, 14 figures

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