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In this work we revisit the question of whether the assumption of a turbulent photosphere provides an efficient mechanism for the disposition of energy in the solar corona. Through a two-dimensional incompressible MHD spectral code and appropriate analysis we investigate the long time statistical behavior of a two-dimensional cross section of a coronal loop. In particular we study the transition to turbulence from a large scale quasi-stationary coherent forcing analyzing the effects of the finite Reynolds and Lundquist numbers and the role of noise in triggering resistive instabilities and subsequent cascades. Simulations of the average energy dissipation and the spectral and spatial distribution at a given time show the self-organization of the loop at large scales via an inverse MHD cascade. To quantify the nonlinearity of the response in the case of constant time forcing, we derive scaling laws against resistivity of the difference between the numerical solution and the linear approximation as well as of the time it takes the system to reach the peak after exceeding the linear approximation solution. We finally comment on the response of the loop also on the most general case of time dependent random forcing comparing with the first case. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Many different nonlinear processes can occur in current sheets following the development of magnetic islands. Two of the most important are the coalescence instability and the secondary, or three-dimensional, instability. In this paper we describe the results of some numerical expriments in which both instabilities are present, in an effort to determine which instability will be dominant. It is our finding that, for a wide variety of initial conditions and parameters, that the secondary instability grows a a faster rate than the coalescence instability. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We extend previous 2D simulation studies of slow solar wind acceleration due to the nonlinear evolution of the instability of the plasma/current sheet above streamers. We include the effects of the melon-seed force due to the overall magnetic field radial gradients on the plasmoid formed by the instability, as well as the subsequent expansion effects using the Expanding Box Model. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]