MODELS OF STATIONARY SIPHON FLOWS IN STRATIFIED, THERMALLY CONDUCTINGCORONAL LOOPS .1. REGULAR SOLUTIONS

We present a detailed hydrodynamic model of stationary siphon flows in a semicircular solar coronal loop of constant cross section, which ta kes into account simultaneously gravity, thermal conduction, radiative losses and a phenomenological heating term. The model has been design ed to provide a tool for insight into coronal loop physics and to help interpretation of the observations of new UV and X-ray instruments. I n order to achieve high reliability of the calculations even close to critical points, we have used two very accurate and independent algori thms, and compared their results. Extensive analytical derivations hav e supplemented numerical calculations to study the characteristics of solutions. We distinguish four classes of solutions: subsonic, critica l, supersonic and unphysical. The characteristics of the solutions spa ce depend significantly on the boundary conditions, for instance super sonic solutions exist only for negative heat flux at the base of the l oop. We have explored thoroughly the space of solutions, and have deri ved scaling laws for subsonic solutions which relate the dynamic press ure p + rhov2, the maximum loop temperature, the loop semilength and t he volumetric heating; such scaling laws extend those of Rosner Tucker & Vaiana (1978) and of Serio et al. (1981) to the siphon flows. Addit ional laws and conditions for various classes of siphon flows are deri ved.