A periodic arcade model for extended EUV filaments

¹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching, Germany e-mail: ula@mpa-garching.mpg.de
² Astronomical Institute, Academy of Sciences of the Czech Republic, 25165 Ondřejov, Czech Republic

Received: 17 May 2005
Accepted: 14 September 2005

Abstract

The extensions of Hα filaments that are observed in EUV spectral lines require the presence of cool material in a large volume surrounding these filaments. This material can only be supported by magnetic fields with dips. Such dips can be generated by a sufficiently strong twisting of magnetic flux tubes. In the present paper we have extended earlier work to more realistic magnetic field configurations that are periodic in the x-direction. We derived approximate equilibria for twisted slender flux tubes and determined the region that contains dips. In addition we investigated the effects on our models of the mass loading due to a heavy prominence. Finally we compared our theoretical models with the EUV – observations. We conclude that these types of models are capable of explaining the basic features of the observations.