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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Ambipolar diffusion is a physical mechanism related to the drift betweencharged and neutral particles in a partially ionized plasma that is key in manydifferent astrophysical systems. However, understanding its effects ischallenging due to basic uncertainties concerning relevant microphysicalaspects and the strong constraints it imposes on the numerical modeling. Ouraim is to introduce a numerical tool that allows us to address complex problemsinvolving ambipolar diffusion in which, additionally, departures fromionization equilibrium are important or high resolution is needed. The primaryapplication of this tool is for solar atmosphere calculations, but the methodsand results presented here may also have a potential impact on otherastrophysical systems. We have developed a new module for the stellaratmosphere Bifrost code that improves its computational capabilities of theambipolar diffusion term in the Generalized Ohm's Law. This module includes,among other things, collision terms adequate to processes in the coolestregions in the solar chromosphere. As a key feature of the module, we haveimplemented the Super Time-Stepping (STS) technique, that allows an importantacceleration of the calculations. We have also introduced hyperdiffusion termsto guarantee the stability of the code. We show that to have an accurate valuefor the ambipolar diffusion coefficient in the solar atmosphere it is necessaryto include as atomic elements in the equation of state not only hydrogen andhelium but also the main electron donors like sodium, silicon and potassium. Inaddition, we establish a range of criteria to set up an automatic selection ofthe free parameters of the STS method that guarantees the best performance,optimizing the stability and speed for the ambipolar diffusion calculations. Wevalidate the STS implementation by comparison with a self-similar analyticalsolution.

Ambipolar diffusion in the Bifrost code