A MODEL FOR THE SOURCES OF THE SLOW SOLAR WIND

Abstract

Models for the origin of the slow solar wind must account for two seemingly\ncontradictory observations: The slow wind has the composition of the closed\nfield corona, implying that it originates from the continuous opening and\nclosing of flux at the boundary between open and closed field. On the other\nhand, the slow wind also has large angular width, up to ~ 60{\\circ}, suggesting\nthat its source extends far from the open-closed boundary. We propose a model\nthat can explain both observations. The key idea is that the source of the slow\nwind at the Sun is a network of narrow (possibly singular) open-field corridors\nthat map to a web of separatrices and quasi-separatrix layers in the\nheliosphere. We compute analytically the topology of an open-field corridor and\nshow that it produces a quasi-separatrix layer in the heliosphere that extends\nto angles far from the heliospheric current sheet. We then use an MHD code and\nMDI/SOHO observations of the photospheric magnetic field to calculate\nnumerically, with high spatial resolution, the quasi-steady solar wind and\nmagnetic field for a time period preceding the August 1, 2008 total solar\neclipse. Our numerical results imply that, at least for this time period, a web\nof separatrices (which we term an S-web) forms with sufficient density and\nextent in the heliosphere to account for the observed properties of the slow\nwind. We discuss the implications of our S-web model for the structure and\ndynamics of the corona and heliosphere, and propose further tests of the model.\n