English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In this study we present a compressible test-field method (CTFM) forcomputing $\alpha$ effect and turbulent magnetic diffusivity tensors, as wellas those relevant for mean ponderomotive force and mass source, applied to thefull MHD equations. We describe the theoretical background of the method, andcompare it to the quasi-kinematic test-field method, and to the previouslystudied variant working in simplified MHD (SMHD). We present several test casesusing velocity and magnetic fields of the Roberts geometry, and also comparewith the imposed-field method. We show that, for moderate imposed fieldstrengths, the nonlinear CTFM (nCTFM) gives results in agreement with theimposed-field method. Comparison of different flavors of the nCTFM in the sheardynamo case also agree up to equipartition field strengths. Some deviationsbetween the CTFM and SMHD variants exist. As a relevant physical application,we study non-helically forced shear flows, which exhibit large-scale dynamoaction, and present a re-analysis of low Reynolds number, moderate shearsystems, where we previously neglected the pressure gradient in the momentumequation, and found no coherent shear-current effect. Another key difference isthat in the earlier study we used magnetic forcing to mimic small-scale dynamoaction, while here it is self-consistently driven by purely kinetic forcing.The kinematic CTFM with general validity forms the core of our analysis. Westill find no coherent shear-current effect, but do recover strong large-scaledynamo action that, according to our analysis, is driven through the incoherenteffects.

Compressible test-field method and its application to shear dynamos