Electron Density Modeling of a Streamer Using LASCO Data of 2004 January and February

Abstract

We present a three-dimensional reconstruction of the electron density of a streamer using a newly developed forward modeling technique. The streamer was observed by SOHO LASCO continuously at the end of 2004 January, but for this study we consider two dates, about 7 days apart. On the first day the streamer was seen "edge-on,'' in which the coronal neutral line was perpendicular to the solar limb and the overlying streamer was quite narrow. The second occurred 7 days later, when the streamer had rotated over the solar pole, and the streamer was now seen "face-on.'' At this time the neutral line was parallel to the polar limb. Using electron density inversion techniques, we have determined the density profiles characterizing the length and thickness of the streamer. Those density profiles were used to refine a three-dimensional model of the streamer belt, approximated by a Gaussian slab. We find good agreement of the radial profile with previous streamer models, but we find that the electron density can vary by 1 order of magnitude within the streamer structure.