3d Numerical Models of the Chromosphere, Transition Region, and Corona

Abstract. A major goal in solar physics has during the last five decadesbeen to find how energy flux generated in the solar convection zone is trans-ported and dissipated in the outer solar layers. Progress in this field has beenslow and painstaking. However, advances in computer hardware and numericalmethods, vastly increased observational capabilities and growingphysical insightseem finally to be leading towards understanding. Here we present exploratorynumerical MHD models that span the entire solar atmosphere from the upperconvection zone to the lower corona. These models include non-grey, non-LTEradiative transport in the photosphere and chromosphere, optically thin radia-tive losses as well as magnetic field-aligned heat conduction in the transitionregion and corona. 1. IntroductionThe notion that chromospheric and coronal heating in some way follow fromexcess “mechanical” energy flux as a result of convective motions has been clearsince the mid-1940’s. Even so, it is only recently that computer power and algo-rithmic developments have allowed one to even consider taking on the dauntingtask of modeling the entire system from convection zone to corona in a singlemodel.Several of these challenges were met during the last few years in the work ofGudiksen & Nordlund (Gudiksen & Nordlund 2002), where it was shown that itis possible to model the photosphere to corona system. In their model a scaleddown longitudinal magnetic field taken from an SOHO/MDI magnetogram ofan active region is used to produce a potential magnetic field in the computa-tional domain that covers 50×50×30 Mm