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Title: Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips

Abstract

Large-amplitude longitudinal oscillations of solar filaments have been observed and explored for more than ten years. Previous studies are mainly based on the one-dimensional rigid flux tube model with a single magnetic dip. However, it has been noted that there might be two magnetic dips, and hence two threads, along one magnetic field line. Following previous work, we intend to investigate the kinematics of the filament longitudinal oscillations when two threads are magnetically connected, which is done by solving one-dimensional radiative hydrodynamic equations with the numerical code MPI-AMRVAC. Two different types of perturbations are considered, and the difference from previous works resulting from the interaction of the two filament threads is investigated. We find that even with the inclusion of the thread–thread interaction, the oscillation period is modified weakly, by at most 20% compared to the traditional pendulum model with one thread. However, the damping timescale is significantly affected by the thread–thread interaction. Hence, we should take it into account when applying the consistent seismology to the filaments where two threads are magnetically connected.

Authors:
; ; ; ;  [1]
  1. School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China)
Publication Date:
OSTI Identifier:
22661171
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 839; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; COHERENT TUBE MODEL; COMPARATIVE EVALUATIONS; DAMPING; DISTURBANCES; EQUATIONS; FILAMENTS; HYDRODYNAMICS; INTERACTIONS; MAGNETIC FIELDS; MECHANICAL VIBRATIONS; ONE-DIMENSIONAL CALCULATIONS; OSCILLATIONS; PERTURBATION THEORY; SEISMOLOGY; SUN; TIME MEASUREMENT

Citation Formats

Zhou Yu-Hao, Zhang Li-Yue, Ouyang, Y., Chen, P. F., and Fang, C., E-mail: chenpf@nju.edu.cn. Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA67DE.
Zhou Yu-Hao, Zhang Li-Yue, Ouyang, Y., Chen, P. F., & Fang, C., E-mail: chenpf@nju.edu.cn. Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips. United States. doi:10.3847/1538-4357/AA67DE.
Zhou Yu-Hao, Zhang Li-Yue, Ouyang, Y., Chen, P. F., and Fang, C., E-mail: chenpf@nju.edu.cn. Mon . "Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips". United States. doi:10.3847/1538-4357/AA67DE.
@article{osti_22661171,
title = {Solar Filament Longitudinal Oscillations along a Magnetic Field Tube with Two Dips},
author = {Zhou Yu-Hao and Zhang Li-Yue and Ouyang, Y. and Chen, P. F. and Fang, C., E-mail: chenpf@nju.edu.cn},
abstractNote = {Large-amplitude longitudinal oscillations of solar filaments have been observed and explored for more than ten years. Previous studies are mainly based on the one-dimensional rigid flux tube model with a single magnetic dip. However, it has been noted that there might be two magnetic dips, and hence two threads, along one magnetic field line. Following previous work, we intend to investigate the kinematics of the filament longitudinal oscillations when two threads are magnetically connected, which is done by solving one-dimensional radiative hydrodynamic equations with the numerical code MPI-AMRVAC. Two different types of perturbations are considered, and the difference from previous works resulting from the interaction of the two filament threads is investigated. We find that even with the inclusion of the thread–thread interaction, the oscillation period is modified weakly, by at most 20% compared to the traditional pendulum model with one thread. However, the damping timescale is significantly affected by the thread–thread interaction. Hence, we should take it into account when applying the consistent seismology to the filaments where two threads are magnetically connected.},
doi = {10.3847/1538-4357/AA67DE},
journal = {Astrophysical Journal},
number = 1,
volume = 839,
place = {United States},
year = {Mon Apr 10 00:00:00 EDT 2017},
month = {Mon Apr 10 00:00:00 EDT 2017}
}
  • A relativistic theory of longitudinal oscillations in hot, magnetized, isotropic equilibrium plasmas is presented. The special theory of relativity enters the description, with the requirements that the particle masses are depending on the particle velocities that themselves are limited by the speed of light. Using the relativistic Maxwell--Boltzmann--Juettner distribution correctly describing the equilibrium state of a plasma, the dispersion relations for subluminal, as well as superluminal waves, are formulated using the Trubnikov representation. Besides a discussion of the dispersion curves, it is shown that superluminal oscillations are always undamped, whereas for subluminal waves the relativistic generalization of the Landau dampingmore » is derived. It is shown that the resulting damping rates are significantly lower than those obtained with the nonrelativistic theory. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
  • We investigate the influence of the geometry of the solar filament magnetic structure on the large-amplitude longitudinal oscillations. A representative filament flux tube is modeled as composed of a cool thread centered in a dipped part with hot coronal regions on either side. We have found the normal modes of the system and establish that the observed longitudinal oscillations are well described with the fundamental mode. For small and intermediate curvature radii and moderate to large density contrast between the prominence and the corona, the main restoring force is the solar gravity. In this full wave description of the oscillationmore » a simple expression for the oscillation frequencies is derived in which the pressure-driven term introduces a small correction. We have also found that the normal modes are almost independent of the geometry of the hot regions of the tube. We conclude that observed large-amplitude longitudinal oscillations are driven by the projected gravity along the flux tubes and are strongly influenced by the curvature of the dips of the magnetic field in which the threads reside.« less
  • We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motionsmore » are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.« less
  • We present the first Solar Dynamics Observatory/Atmospheric Imaging Assembly observations of the large-amplitude longitudinal (LAL) oscillations in the south and north parts (SP and NP) of a solar filament on 2012 April 7. Both oscillations are triggered by flare activities close to the filament. The period varies with filamentary threads, ranging from 44 to 67 minutes. The oscillations of different threads are out of phase, and their velocity amplitudes vary from 30 to 60 km s{sup -1}, with a maximum displacement of about 25 Mm. The oscillations of the SP repeat for about four cycles without any significant damping andmore » then a nearby C2.4 flare causes the transition from the LAL oscillations of the filament to its later eruption. The filament eruption is also associated with a coronal mass ejection and a B6.8 flare. However, the oscillations of the NP damp with time and die out at last. Our observations show that the activated part of the SP repeatedly shows a helical motion. This indicates that the magnetic structure of the filament is possibly modified during this process. We suggest that the restoring force is the coupling of the magnetic tension and gravity.« less
  • On 2010 August 20, an energetic disturbance triggered large-amplitude longitudinal oscillations in a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. In the present work, we analyze this periodic motion in a large fraction of the filament to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we usedmore » the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of cohesiveness throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We estimate the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and discuss the implications of our study for filament structure and heating.« less