Abstract
Abstract. We study a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian and Vishniac (1999) using three-dimensional direct numerical simulations. The model has been already successfully tested in Kowal et al. (2009) confirming the dependencies of the reconnection speed Vrec on the turbulence injection power Pinj and the injection scale linj expressed by a constraint Vrec ~ Pinj1/2linj3/4and no observed dependency on Ohmic resistivity. In Kowal et al. (2009), in order to drive turbulence, we injected velocity fluctuations in Fourier space with frequencies concentrated around kinj = 1/linj, as described in Alvelius (1999). In this paper, we extend our previous studies by comparing fast magnetic reconnection under different mechanisms of turbulence injection by introducing a new way of turbulence driving. The new method injects velocity or magnetic eddies with a specified amplitude and scale in random locations directly in real space. We provide exact relations between the eddy parameters and turbulent power and injection scale. We performed simulations with new forcing in order to study turbulent power and injection scale dependencies. The results show no discrepancy between models with two different methods of turbulence driving exposing the same scalings in both cases. This is in agreement with the Lazarian and Vishniac (1999) predictions. In addition, we performed a series of models with varying viscosity ν. Although Lazarian and Vishniac (1999) do not provide any prediction for this dependence, we report a weak relation between the reconnection speed with viscosity, Vrec ~ ν−1/4.
Highlights
Magnetic fields are observed in many astrophysical objects and usually play an important or even crucial role in their dynamics
In the limit of very small resistivity, which is typical for astrophysical objects, the magnetic flux is “frozen in” and magnetic field lines will resist passing through one another or changing their topology (Moffat, 1978)
We have introduced a new method of driving turbulence by direct injection of the velocity or magnetic eddies with random locations in the domain
Summary
Magnetic fields are observed in many astrophysical objects and usually play an important or even crucial role in their dynamics (see, e.g. Crutcher, 1999; Beck, 2002; Vallee, 1997, 1998). In the limit of very small resistivity, which is typical for astrophysical objects, the magnetic flux is “frozen in” and magnetic field lines will resist passing through one another or changing their topology (Moffat, 1978). Observations indicate that the mean and turbulent components of magnetic fields in many astrophysical objects are of similar strengths (see Beck, 2002, for example). This implies the existence of a process which can violate the frozen-in condition on dynamical time scales, i.e., fast magnetic field reconnection
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call