Letter to the Editor

Excitation of vertical coronal loop oscillations by impulsively driven flows

Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
e-mail: p.kohutova@warwick.ac.uk

Received: 17 January 2018
Accepted: 23 April 2018

Abstract

Context. Flows of plasma along a coronal loop caused by the pressure difference between loop footpoints are common in the solar corona.

Aims. We aim to investigate the possibility of excitation of loop oscillations by an impulsively driven flow triggered by an enhanced pressure in one of the loop footpoints.

Methods. We carry out 2.5D magnetohydrodynamic (MHD) simulations of a coronal loop with an impulsively driven flow and investigate the properties and evolution of the resulting oscillatory motion of the loop.

Results. The action of the centrifugal force associated with plasma moving at high speeds along the curved axis of the loop is found to excite the fundamental harmonic of a vertically polarised kink mode. We analyse the dependence of the resulting oscillations on the speed and kinetic energy of the flow.

Conclusions. We find that flows with realistic speeds of less than 100 km s⁻¹ are sufficient to excite oscillations with observable amplitudes. We therefore propose plasma flows as a possible excitation mechanism for observed transverse loop oscillations.