Test-field method for mean-field coefficients with MHD background

Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

17 pages, 10 figures, submitted to Astronomy & Astrophysics

Scientific paper

10.1051/0004-6361/201014700

Aims: The test-field method for computing turbulent transport coefficients from simulations of hydromagnetic flows is extended to the regime with a magnetohydrodynamic (MHD) background. Methods: A generalized set of test equations is derived using both the induction equation and a modified momentum equation. By employing an additional set of auxiliary equations, we derive linear equations describing the response of the system to a set of prescribed test fields. Purely magnetic and MHD backgrounds are emulated by applying an electromotive force in the induction equation analogously to the ponderomotive force in the momentum equation. Both forces are chosen to have Roberts flow-like geometry. Results: Examples with an MHD background are studied where the previously used quasi-kinematic test-field method breaks down. In cases with homogeneous mean fields it is shown that the generalized test-field method produces the same results as the imposed-field method, where the field-aligned component of the actual electromotive force from the simulation is used. Furthermore, results for the turbulent diffusivity tensor are given, which are inaccessible to the imposed-field method. For MHD backgrounds, new mean-field effects are found that depend on the occurrence of cross-correlations between magnetic and velocity fluctuations. For strong imposed fields, $\alpha$ is found to be quenched proportional to the fourth power of the field strength, regardless of the type of background studied.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

Test-field method for mean-field coefficients with MHD background does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Test-field method for mean-field coefficients with MHD background, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Test-field method for mean-field coefficients with MHD background will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-637654

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.