EDP Sciences
Free access
Volume 437, Number 3, July III 2005
Page(s) 1081 - 1092
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20052745

A&A 437, 1081-1092 (2005)
DOI: 10.1051/0004-6361:20052745

Siphon flows and oscillations in long coronal loops due to Alfvén waves

R. Grappin1, J. Léorat1 and S. Rifai Habbal2, 3

1  Observatoire de Paris-Meudon, 1 place J. Janssen, 92195 Meudon Cedex, France
    e-mail: [roland.grappin;jacques.leorat]@obspm.fr
2  University of Wales, Aberystwyth SY23 3BZ, UK
3  Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
    e-mail: sdh@aber.ac.uk

(Received 21 January 2005 / Accepted 16 March 2005)

Using an isothermal axisymmetric MHD model of the solar corona with transparent boundary conditions, we study how coronal loops with apex height between one third and two solar radii react to Alfvén waves generated at the base of the corona. The first response is a steady increase of the density along the excited loops. Density oscillations are also observed, along the apex of the longest loops, that is, those along which waves are substantially damped. Both the steady and the oscillating component scale as the square of the Alfvén wave amplitude, and accordingly, the frequency is double that of the mother wave. Siphon flows may also appear, along short or long loops, depending on whether both or a single foot-point of the loop system is excited.

Key words: Sun: corona -- methods: numerical -- magnetohydrodynamics (MHD)

© ESO 2005