Motivation and challenge to capture both large scale and local transport in next generation accretion theory

摘要: Accretion disc theory is less developed than stellar evolution although a similarly mature phenomenological picture ultimately desired. While the interplay of and numerical simulations has amplified community awareness role magnetic fields in angular momentum transport, there remains long term challenge to incorporate insight gained from back into improving practical models for comparison with observations. Here we emphasize need non-local transport more precisely. To show where large scale would fit theoretical framework how it currently missing, review why wonderfully approach Shakura-Sunyaev (1973,SS73) necessarily mean field theory, one which does not include transport. Observations coronae jets combined interpretation results even shearing box magnetorotational instability (MRI) suggest that significant fraction indeed non-local. We Maxwell stresses saturation are dominated by contributions physics MRI fully captured viscosity. also clarify standard physical MRi as applies boxes. Computational limitations have so far focused most attention toward local but next generation global should help inform improved theories. Mean accretion dynamo fact be unified single predicts time spectra luminosity separate disc, corona, outflow contributions. Finally, note any finite predictive precision needs quantified when comparing predictions