Simulation of Large-Scale Flows at the Solar Surface.

摘要

A simple analytic axisymmetric function will represent the radial outflow associated with an isolated convection plume at the solar surface. The vertical velocity can be deduced from the continuity equation. A regular cellular pattern of convection can be created by superposing a number of such sources. Our motivation for this study came from the large-scale horizontal motions observed by the SOUP instrument on Spacelab 2. The flow pattern is simulated as visible in three different regions covered by the SOUP observations. In each case a superposition of our plume functions mimics the observed mesogranular and supergranular motions remarkably well. The model can be improved by using the same procedure to represent sinks as well as sources in the observed velocity field. We use these model flows to compute the motion of passive test particles (corks) which accumulate in a network that outlines mesogranular cells. The cork patterns closely resemble the magnetic network observed at the time of the SOUP measurements. Detailed comparisons suggest that magnetic flux tubes are affected more by outflow from sources at the centers of mesogranules than by flow into sinks within the network. Keywords: Reprints; Solar convection; Solar atmosphere; Solar granulation. (jhd)