Observations and simulations of longitudinal oscillations of an active region prominence

Zhang, Q M; Chen, P. F.; Xia, Chun; Keppens, Rony

doi:10.1051/0004-6361/201218786

Cited by 95 publications

(143 citation statements)

References 45 publications

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“…(12) can be roughly measured. Combined with the results in this paper, the comparison between simulations and observations in Zhang et al (2012) implies that Eq. (12) is a good approximation for estimating the oscillation period.…”

Section: Restoring Forcesupporting

confidence: 75%

“…4. This result, namely that mass drainage would greatly reduce the decay timescale, might explain the mismatch between the simulation and the observation of the decay of a prominence oscillation reported in Zhang et al (2012).…”

Section: Damping Mechanismsmentioning

confidence: 77%

“…The single decayed sine function used for fitting the Hα observations (Jing et al 2003;Vršnak et al 2007;Zhang et al 2012) fits the simulated observations very well. In contrast, a combination of Bessel function and an exponential decay function is necessary to fit the initial overtone in the simulations of Luna & Karpen (2012), which results from the continual mass accumulation.…”

Section: Effects Of the Perturbation Typementioning

confidence: 79%

“…More damping mechanisms have been proposed, such as thermal conduction, radiation, ion-neutral collisions, resonant absorption, and wave leakage (see Tripathi et al 2009 andArregui et al 2012, for reviews). For the longitudinal oscillations, Zhang et al (2012) found that non-adiabatic terms such as the radiation and the heat conduction contribute to the damping, but they might not be sufficient to explain the observed shorter timescale. In their simulations the chromospheric heating was switched off, so that the prominence mass was nearly fixed.…”

Section: Introductionmentioning

confidence: 97%

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Parametric survey of longitudinal prominence oscillation simulations

Zhang

Chen

Xia

et al. 2013

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Context. Longitudinal filament oscillations recently attracted increasing attention, while the restoring force and the damping mechanisms are still elusive. Aims. 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. Methods. With the MPI-AMRVAC code, we carried out radiative hydrodynamic numerical simulations of the longitudinal prominence oscillations. We modeled two types of perturbations of the prominence, impulsive heating at one leg of the loop and an impulsive momentum deposition, which cause the prominence to oscillate. We studied the resulting oscillations for a large parameter scan, including the chromospheric heating duration, initial velocity of the prominence, and field line geometry. Results. We 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. Our extensive parameter survey resulted in a scaling law that shows that the period of the oscillation, which weakly depends on the length and height of the prominence and on the amplitude of the perturbations, scales with R/g , where R represents the curvature radius of the dip, and g 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 significant for short prominences. The oscillation damps with time in the presence of non-adiabatic processes. Radiative cooling is the dominant factor leading to damping. A scaling law for the damping timescale is derived, i.e., τ ∼ l 1.63 D 0.66 w −1.21 v −0.30 0 , 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. We also found that mass drainage significantly reduces the damping timescale when the perturbation is too strong.

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Section: Restoring Forcesupporting

confidence: 75%

Section: Damping Mechanismsmentioning

confidence: 77%

Section: Effects Of the Perturbation Typementioning

confidence: 79%

Section: Introductionmentioning

confidence: 97%

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Parametric survey of longitudinal prominence oscillation simulations

Zhang

Chen

Xia

et al. 2013

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“…These numbers indicate that the oscillation damping was very strong. More events have since been reported by Jing et al (2006), Vršnak et al (2007), Zhang et al (2012), Li & Zhang (2012), Luna et al (2014), Bi et al (2014), and Shen et al (2014). The range of the velocity amplitude was between 20 and 100 km s −1 , the period between 40 and 160 min, and the damping time between 1 and 3.8 periods.…”

Section: Introductionmentioning

confidence: 91%

Damping of prominence longitudinal oscillations due to mass accretion

Luna

2016

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We study the damping of longitudinal oscillations of a prominence thread caused by the mass accretion. We suggested a simple model describing this phenomenon. In this model we considered a thin curved magnetic tube filled with the plasma. The prominence thread is in the central part of the tube and it consists of dense cold plasma. The parts of the tube at the two sides of the thread are filled with hot rarefied plasma. We assume that there are flows of rarefied plasma toward the thread caused by the plasma evaporation at the magnetic tube footpoints. Our main assumption is that the hot plasma is instantaneously accommodated by the thread when it arrives at the thread, and its temperature and density become equal to those of the thread. Then we derive the system of ordinary differential equations describing the thread dynamics. We solve this system of ordinary differential equations in two particular cases. In the first case we assume that the magnetic tube is composed of an arc of a circle with two straight lines attached to its ends such that the whole curve is smooth. A very important property of this model is that the equations describing the thread oscillations are linear for any oscillation amplitude. We obtain the analytical solution of the governing equations. Then we obtain the analytical expressions for the oscillation damping time and periods. We find that the damping time is inversely proportional to the accretion rate. The oscillation periods increase with time. We conclude that the oscillations can damp in a few periods if the inclination angle is sufficiently small, not larger that 10 • , and the flow speed is sufficiently large, not less that 30 km s −1 . In the second model we consider the tube with the shape of an arc of a circle. The thread oscillates with the pendulum frequency dependent exclusively on the radius of curvature of the arc. The damping depends on the mass accretion rate and the initial mass of the threads, that is the mass of the thread at the moment when it is perturbed. First we consider small amplitude oscillations and use the linear description. Then we consider nonlinear oscillations and assume that the damping is slow, meaning that the damping time is much larger that the characteristic oscillation time. The thread oscillations are described by the solution of the nonlinear pendulum problem with slowly varying amplitude. The nonlinearity reduces the damping time, however this reduction is small. Again the damping time is inversely proportional to the accretion rate. We also obtain that the oscillation periods decrease with time. However even for the largest initial oscillation amplitude considered in our article the period reduction does not exceed 20%. We conclude that the mass accretion can damp the motion of the threads rapidly. Thus, this mechanism can explain the observed strong damping of large-amplitude longitudinal oscillations. In addition, the damping time can be used to determine the mass accretion rate and indirectly the coronal heating.

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