Attenuation of Alfvén waves in straight and curved coronal slabs

¹ Group of Astrophysics and Gravity Theory, Institute of Physics, UMCS, ul. Radziszewskiego 10, 20-031 Lublin, Poland e-mail: marcingruszecki@wp.pl
² Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
³ The Catholic University of America, NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771, USA

Received: 12 December 2006
Accepted: 28 March 2007

Abstract

Aims.We consider impulsively generated Alfvén waves in coronal loops to investigate the role of energy leakage on wave attenuation, which includes lateral leakage, leakage into dense photospheric regions and nonlinear driving of magnetosonic waves.

Methods.A coronal loop is modelled either as a straight magnetic slab or as a curved slab of smooth mass density profiles. We perform numerical simulations of 2.5D ideal magnetohydrodynamic equations to determine the signatures of Alfvén waves.

Results.The numerical results show that lateral leakage of Alfvén waves is significant in comparison to leakage into the photospheric regions for realistic corona to photospheric density ratios. Energy leakage is enhanced by curvature of magnetic field lines and for large amplitude Alfvén waves for which nonlinear driving of magnetosonic waves is more significant than in the linear regime.