Determination of the 3D-topology of an EUV-filament observed by SoHO/CDS SoHO/SUMER and VTT/MSDP

TitleDetermination of the 3D-topology of an EUV-filament observed by SoHO/CDS SoHO/SUMER and VTT/MSDP
Publication TypeConference Paper
Year of Publication2003
AuthorsSchwartz, P., Heinzel P., Schmieder B., and Anzer U.
EditorWilson, A.
Conference NameSolar Variability as an Input to the Earth's Environment
Date PublishedSep
Abstract

We have constructed a spatial model of an extended EUV-filament observed on 15 October 1999 (polar crown N 38 deg) by SoHO/CDS. The narrow Hα counterparts were observed by VTT/MSDP. As found in 2001, EUV-filaments are much more extended than those parts visible in Hα. We have computed the bottom and top heights of this EUV-filament for the whole CDS raster for different values of the Lyman-continuum optical thickness using CDS measurements of two coronal lines (Mg X 624.94 Å and Si XII 520.60 Å) and the model of Heinzel et al., 2003. For the scale height of the MgX line we used the value from Fludra et al. 1999, assuming that this line is not solar cycle and activity dependent. We created a new method for τ$_{912}$ determination from O VI and O V line intensities. Because of the inhomogeneity in the O V 629.37 Å line intensity distribution in the vicinitiy of the EUV-filament it was not possible to estimate this intensity under the filament. So we used observations made by SoHO/SUMER of the O VI 1031.91 Å line not absorbed by EUV-filament cold plasma. The knowledge of the heights of the bottom and top boundaries of an EUV-filament gives us the EUV-filament geometrical thickness. From this the mass of the EUV-filament was computed.