%0 Generic %1 citeulike:13800853 %A Ross, Johnathan %A Latter, Henrik N. %A Guilet, Jerome %D 2015 %K imported %T The stress-pressure relationship in simulations of MRI-induced turbulence %U http://arxiv.org/abs/1510.01214 %X We determine how MRI-turbulent stresses depend on gas pressure via a suite of unstratified shearing box simulations. Earlier numerical work reported only a very weak dependence at best, results that call into question the canonical alpha-disk model and the thermal stability results that follow from it. Our simulations, in contrast, exhibit a stronger relationship, and show that previous work was box-size limited: turbulent `eddies' were artificially restricted by the numerical domain rather than by the scale height. Zero-net-flux runs without physical diffusion coefficients yield a stress proportional to \$P^0.5\$, where P is pressure. The stresses are also proportional to the grid length and hence remain numerically unconverged. The same runs with physical diffusivities, however, give a result closer to an alpha-disk: the stress is proportional to \$P^0.9\$. Net-flux simulations without explicit diffusion exhibit stresses proportional to \$P^0.5\$, but stronger imposed fields weaken this correlation. In summary, compressibility is important for the saturation of the MRI, but the exact stress-pressure relationship is difficult to ascertain in local simulations because of numerical convergence issues and the influence of any imposed flux. As a consequence, the interpretation of thermal stability behaviour in local simulations is a problematic enterprise.

@misc{citeulike:13800853, abstract = {We determine how MRI-turbulent stresses depend on gas pressure via a suite of unstratified shearing box simulations. Earlier numerical work reported only a very weak dependence at best, results that call into question the canonical alpha-disk model and the thermal stability results that follow from it. Our simulations, in contrast, exhibit a stronger relationship, and show that previous work was box-size limited: turbulent `eddies' were artificially restricted by the numerical domain rather than by the scale height. Zero-net-flux runs without physical diffusion coefficients yield a stress proportional to \$P^{0.5}\$, where P is pressure. The stresses are also proportional to the grid length and hence remain numerically unconverged. The same runs with physical diffusivities, however, give a result closer to an alpha-disk: the stress is proportional to \$P^{0.9}\$. Net-flux simulations without explicit diffusion exhibit stresses proportional to \$P^{0.5}\$, but stronger imposed fields weaken this correlation. In summary, compressibility is important for the saturation of the MRI, but the exact stress-pressure relationship is difficult to ascertain in local simulations because of numerical convergence issues and the influence of any imposed flux. As a consequence, the interpretation of thermal stability behaviour in local simulations is a problematic enterprise.}, added-at = {2019-03-25T08:20:55.000+0100}, archiveprefix = {arXiv}, author = {Ross, Johnathan and Latter, Henrik N. and Guilet, Jerome}, biburl = {https://www.bibsonomy.org/bibtex/2507e1cc400184399a96320e75a7533ee/ericblackman}, citeulike-article-id = {13800853}, citeulike-linkout-0 = {http://arxiv.org/abs/1510.01214}, citeulike-linkout-1 = {http://arxiv.org/pdf/1510.01214}, day = 5, eprint = {1510.01214}, interhash = {186a4bb3e708b98e9a00fce37c1eb110}, intrahash = {507e1cc400184399a96320e75a7533ee}, keywords = {imported}, month = oct, posted-at = {2015-10-12 22:08:54}, priority = {2}, timestamp = {2019-03-25T08:20:55.000+0100}, title = {{The stress-pressure relationship in simulations of MRI-induced turbulence}}, url = {http://arxiv.org/abs/1510.01214}, year = 2015 }