Excitation of vertical kink waves in a solar coronal arcade loop by a periodic driver

¹ Department of Physics, The Catholic University of America, 620 Michigan Avenue, NE, 200 Hannan Hall, Washington, DC 20064; NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771, USA e-mail: mselwa@helio.gsfc.nasa.gov
² Group of Astrophysics and Gravity Theory, Institute of Physics, UMCS, ul. Radziszewskiego 10, 20-031 Lublin, Poland
³ Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
⁴ School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701, Korea

Received: 29 May 2009
Accepted: 21 October 2009

Abstract

Aims. We study an oscillatory driver as a possible excitation mechanism of vertical kink loop oscillations in the ideal MHD regime.

Methods. We consider a solar coronal magnetic arcade with a dense photospheric layer. The two-dimensional numerical model that we implement includes the effects of nonlinearity and line curvature on the excitation and attenuation of fast magnetosonic kink waves. We investigate the effects of a driven sinusoidal pressure pulse and compare it with the impulsive excitation by a pressure pulse that impacts the overlying loop.

Results. Our numerical simulations reveal wave signatures that are reminiscent of vertical loop oscillations seen in TRACE observational data.

Conclusions. We conclude that attenuation of vertical kink oscillations can be reduced to the value observed by adopting an oscillatory instead of an impulsive excitation. An oscillatory driver also naturally explains why only a small subset of all loops is excited to oscillate transversally in an active region.