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

We examine the nonlinear magnetofrictional extrapolation scheme using thesolar active region model by Titov and D\'emoulin as test field. This modelconsists of an arched, line-tied current channel held in force-free equilibriumby the potential field of a bipolar flux distribution in the bottom boundary. Amodified version, having a parabolic current density profile, is employed here.We find that the equilibrium is reconstructed with very high accuracy in arepresentative range of parameter space, using only the vector field in thebottom boundary as input. Structural features formed in the interface betweenthe flux rope and the surrounding arcade-"hyperbolic flux tube" and "bald patchseparatrix surface"-are reliably reproduced, as are the flux rope twist and theenergy and helicity of the configuration. This demonstrates that force-freefields containing these basic structural elements of solar active regions canbe obtained by extrapolation. The influence of the chosen initial condition onthe accuracy of reconstruction is also addressed, confirming that the initialfield that best matches the external potential field of the model quitenaturally leads to the best reconstruction. Extrapolating the magnetogram of aTitov-D\'emoulin equilibrium in the unstable range of parameter space yields asequence of two opposing evolutionary phases which clearly indicate theunstable nature of the configuration: a partial buildup of the flux rope withrising free energy is followed by destruction of the rope, losing most of thefree energy.

Testing magnetofrictional extrapolation with the Titov-D\'emoulin model of solar active regions