Snodin, A. P., Ruffolo, D., Oughton, S., Servidio, S., & Matthaeus, W. H. (2013). Magnetic field line random walk in models and simulations of reduced magnetohydrodynamic turbulence. The Astrophysical Journal, 779(1), 56.
Permanent Research Commons link: http://hdl.handle.net/10289/8587
The random walk of magnetic ﬁeld lines is examined numerically and analytically in the context of reduced magnetohydrodynamic (RMHD) turbulence, which provides a useful description of plasmas dominated by a strong mean ﬁeld, such as in the solar corona. A recently developed non-perturbative theory of magnetic ﬁeld line diffusion is compared with the diffusion coefﬁcients obtained by accurate numerical tracing of magnetic ﬁeld lines for both synthetic models and direct numerical simulations of RMHD. Statistical analysis of an ensemble of trajectories conﬁrms the applicability of the theory, which very closely matches the numerical ﬁeld line diffusion coefﬁcient as a function of distance z along the mean magnetic ﬁeld for a wide range of the Kubo number R. This theory employs Corrsin’s independence hypothesis, sometimes thought to be valid only at low R. However, the results demonstrate that it works well up to R = 10, both for a synthetic RMHD model and an RMHD simulation. The numerical results from the RMHD simulation are compared with and without phase randomization, demonstrating a clear effect of coherent structures on the ﬁeld line random walk for a very low Kubo number.
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