Parametric survey of longitudinal prominence oscillation simulations 

Qingmin Zhang Submitted: 20130416 02:58
{Longitudinal filament oscillations recently attracted more and more
attention, while the restoring force and the damping mechanisms are still
elusive.}
{In this paper, we intend to investigate the underlying
physics for coherent longitudinal oscillations of the entire
filament body, including their triggering mechanism, dominant
restoring force, and damping mechanisms.}
{With the MPIAMRVAC code, we carry out radiative hydrodynamic
numerical simulations of the longitudinal prominence oscillations. Two
types of perturbations, i.e., impulsive heating at one leg of the loop
and an impulsive momentum deposition are introduced to the prominence,
which then starts to oscillate. We study the resulting oscillations for a
large parameter scan, including the chromospheric heating duration,
initial velocity of the prominence, and field line geometry.}
{It is found that both microflaresized impulsive heating at one leg of the
loop and a suddenly imposed velocity perturbation can propel the prominence
to oscillate along the magnetic dip. An extensive parameter survey results
in a scaling law, showing that the period of the oscillation, which weakly
depends on the length and height of the prominence, and the amplitude of the
perturbations, scales with sqrt{R/g_odot}, where R represents the
curvature radius of the dip, and g_odot is the gravitational acceleration
of the Sun. This is consistent with the linear theory of a pendulum, which
implies that the fieldaligned component of gravity is the main
restoring force for the prominence longitudinal oscillations, as confirmed
by the force analysis. However, the gas pressure gradient becomes
nonnegligible for short prominences. The oscillation damps with time in
the presence of nonadiabatic processes. Compared to heat conduction,
the radiative cooling is the dominant factor leading to the damping. A
scaling law for the damping timescale is derived, i.e., ausim l^{1.63}
D^{0.66}w^{1.21}v_{0}^{0.30}, showing strong dependence on the
prominence length l, the geometry of the magnetic dip (characterized by
the depth D and the width w), and the velocity perturbation amplitude
v_{0}. The larger the amplitude, the faster the oscillation damps. It is
also found that mass drainage significantly reduces the damping timescale
when the perturbation is too strong.}
Authors: Q. M. Zhang, P .F. Chen, C. Xia, R. Keppens, H. S. Ji
Projects: None

Publication Status: A&A in press
Last Modified: 20130417 12:23


