On a mechanism of intensification of field-aligned currents at the solar chromosphere-quiescent prominence boundaries

¹ Institute of Geophysics Acad. G. Bonchev Str., Bl. 3, 1113 Sofia, Bulgaria
² Institute of Astronomy, 72 Tzarigradsko chaussee Blvd., 1784 Sofia, Bulgaria and Isaac Newton Institute of Chile Bulgarian Branch (Prof. Dermendjiev deceased on January 2001)
³ Institut d'Astrophysique Spatiale, Université Paris XI-CNRS, Bât. 121, 91405 Orsay Cedex, France e-mail: vial@medoc-ias.u-psud.fr; bocchialini@medoc-ias.u-psud.fr

Corresponding author: P. Nenovski, nenovski@geophys.bas.bg

Received: 1 September 2000
Accepted: 15 June 2001

Abstract

Field-aligned electric currents (FAC) are assumed to support various prominence configurations and it is usually supposed that the quiescent prominence (QP) destabilisation can be initiated by some plasma instability. In this work we study another possibility of QP destabilisation connected with FAC changes. Such a destabilisation may occur when FAC flowing along a loop-shaped QP structure are intensified by bouncing surface MHD modes, presumably generated by motions in the photosphere under, or adjacent to, the QP. The MHD disturbances at the prominence "feet" propagate upwards as Alfven waves and surface modes. We study the possibility that the generated MHD modes, which carry FAC, bounce in the loop-shaped QP structure, provided that they undergo multiple reflection at the prominence feet. This is an interesting physical situation leading to intensification of FAC and promising to be another source of QP destabilisation.