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/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

The ideal MHD equations are a central model in astrophysics, and theirsolution relies upon stable numerical schemes. We present an implementation ofa new method, which possesses excellent stability properties. Numerical testsdemonstrate that the theoretical stability properties are valid in practicewith negligible compromises to accuracy. The result is a highly robust schemewith state-of-the-art efficiency. The scheme's robustness is due to entropystability, positivity and properly discretised Powell terms. The implementationtakes the form of a modification of the MHD module in the FLASH code, anadaptive mesh refinement code. We compare the new scheme with the standardFLASH implementation for MHD. Results show comparable accuracy to standardFLASH with the Roe solver, but highly improved efficiency and stability,particularly for high Mach number flows and low plasma beta. The tests include1D shock tubes, 2D instabilities and highly supersonic, 3D turbulence. Weconsider turbulent flows with RMS sonic Mach numbers up to 10, typical of gasflows in the interstellar medium. We investigate both strong initial magneticfields and magnetic field amplification by the turbulent dynamo from extremelyhigh plasma beta. The energy spectra show a reasonable decrease in dissipationwith grid refinement, and at a resolution of 512^3 grid cells we identify anarrow inertial range with the expected power-law scaling. The turbulent dynamoexhibits exponential growth of magnetic pressure, with the growth rate twice ashigh from solenoidal forcing than from compressive forcing. Two versions of thenew scheme are presented, using relaxation-based 3-wave and 5-wave approximateRiemann solvers, respectively. The 5-wave solver is more accurate in somecases, and its computational cost is close to the 3-wave solver.

A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests