Parametric survey of longitudinal prominence oscillation simulations

TL;DR

This study conducts a parametric survey of longitudinal prominence oscillations, deriving scaling laws for oscillation periods and damping timescales, and confirms gravity as the main restoring force with radiative cooling as the dominant damping mechanism.

Contribution

It provides new scaling laws for prominence oscillation periods and damping timescales based on extensive simulations, linking physical parameters to observable oscillation characteristics.

Findings

Oscillation period scales with the square root of the dip curvature radius divided by solar gravity.

Radiative cooling dominates the damping process over heat conduction.

Mass drainage accelerates damping when perturbations are strong.

Abstract

It is found that both microflare-sized 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 field-aligned 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 non-negligible for short prominences. The oscillation damps with time in the presence of non-adiabatic 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., $\tau\sim l^{1.63} D^{0.66}w^{-1.21}v_{0}^{-0.30}$, 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.