An empirical 3D model of the large-scale coronal structure based on the distribution of Hα filaments on the solar disk

Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA e-mail: hmorgan@ifa.hawaii.edu

Received: 29 September 2006
Accepted: 4 December 2006

Abstract

Context.Despite the wealth of solar data currently available, the explicit connection between coronal streamers and features on the solar disk remains unresolved.

Aims.To reproduce the large-scale coronal structure starting from the solar surface, an empirical three-dimensional (3D) model is used to test the assumption that such structure, namely streamers, is a consequence of twisted high-density sheets originating from prominences (or, equivalently, filaments) at the base of the corona.

Methods.A 3D model is created whereby high-density sheets are placed above filaments on the solar disk, which twist and merge with height into a final radial configuration constrained by the oberved position of streamers stalks higher up in the corona. The observational constraints are provided by white light observations from the LASCO/C2 data during the declining phase of solar activity, spanning the end of Carrington Rotation (CR) 2005 and the start of CR 2006, i.e. July–August 2003, and the position of filaments from the corresponding Hα synoptic maps of the Paris-Meudon Observatory.

Results.The 3D model thus derived yields a reasonable agreement with the observed large-scale coronal structure, in particular the shape of large helmet streamers.

Conclusions.These results give confidence in the underlying assumption that large helmet streamers can be the result of the convergence of two or more sheet-like structures originating from a distribution of filaments on the solar disk. The model supports the view that streamers, during that time of the solar cycle, are often associated with multiple current sheets.