Dynamics of solar coronal loops

Müller, D.; Peter, Hardi; Hansteen, V. H.

doi:10.1051/0004-6361:20040403

Cited by 146 publications

(172 citation statements)

References 17 publications

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“…Bakhareva et al (1992) showed that plasma partial ionisation causes dynamic regimes to exist in a prominence, which extends the range of oscillation periods. Numerical studies of prominence condensations (Karpen et al 2001;Müller et al 2004) have revealed mass cyclic variations with time periods similar to our observations. As yet, no observational study was carried out to confirm their existence.…”

Section: Discussionsupporting

confidence: 87%

“…The periods obtained by Karpen et al (2001) were 22 h and 15.3 h for loops of length 340 Mm and 180 Mm respectively. Müller et al (2004) found periods near 11 h for a loop of length 100 Mm. The possible interpretation of our observations suggests that the spatial and time evolution of emission above and surrounding the EUV filament reflects the evolution of the corona and condensation masses.…”

Section: Discussionmentioning

confidence: 96%

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Detection of ultra-long-period oscillations in an EUV filament

Foullon¹,

Verwichte²,

Nakariakov³

2004

A&A

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Abstract. We report the first detection of long-period (8-27 h) oscillatory intensity variations in a coronal filament. The filament is observed continuously as it crosses the solar disk in a 12-min-cadence SoHO/EIT 195 Å uninterrupted data set. Cyclic intensity variations are found to be correlated along the filament, while the most pronounced oscillations are detected at its southern end for nearly 6 days. The dominant period of these oscillations is 12.1 h and the amplitude of the intensity variations reaches approximately 10% of the background intensity. The ultra-long-period oscillations may be interpreted in terms of slow string MHD modes or may be connected with thermal over-stability associated with peculiarities of the cooling/heating function and with the effect of neutrals. These theoretical predictions however do not explain the spatial structure of the oscillations along the filament.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 96%

Detection of ultra-long-period oscillations in an EUV filament

Foullon¹,

Verwichte²,

Nakariakov³

2004

A&A

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“…In this late phase the dominant heating of the apex is due to heat conduction from the sides. Potentially, such situations can lead to a loss of equilibrium and catastrophic cooling (Müller et al 2003(Müller et al , 2004), which we do not observe here because the heating is not concentrated strongly enough towards the footpoints. In 3D models with a more stable magnetic field configuration, the loop can reach a (quasi-)equilibrium state, and remain stable for a longer time (Peter & Bingert 2012).…”

Section: Cooling Phasementioning

confidence: 74%

A model for the formation of the active region corona driven by magnetic flux emergence

Chen

Peter

Bingert

et al. 2014

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Aims. We present the first model that couples the formation of the corona of a solar active region to a model of the emergence of a sunspot pair. This allows us to study when, where, and why active region loops form, and how they evolve. Methods. We use a 3D radiation magnetohydrodynamics (MHD) simulation of the emergence of an active region through the upper convection zone and the photosphere as a lower boundary for a 3D MHD coronal model. The coronal model accounts for the braiding of the magnetic fieldlines, which induces currents in the corona to heat up the plasma. We synthesize the coronal emission for a direct comparison to observations. Starting with a basically field-free atmosphere we follow the filling of the corona with magnetic field and plasma. Results. Numerous individually identifiable hot coronal loops form, and reach temperatures well above 1 MK with densities comparable to observations. The footpoints of these loops are found where small patches of magnetic flux concentrations move into the sunspots. The loop formation is triggered by an increase in upward-directed Poynting flux at their footpoints in the photosphere. In the synthesized extreme ultraviolet (EUV) emission these loops develop within a few minutes. The first EUV loop appears as a thin tube, then rises and expands significantly in the horizontal direction. Later, the spatially inhomogeneous heat input leads to a fragmented system of multiple loops or strands in a growing envelope.

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“…By using the width of the line in Hα as a proxy, Antolin and Rouppe van der Voort (2012) give upper limits for Hα coronal rain centered around 7000 K but with a long tail to higher temperatures up to 5 × 10 4 K. It has not been possible to measure densities directly so far, but estimates are made based on numerical simulations of the phenomenon (Müller, Hansteen, and Peter 2003;Müller, Peter, and Hansteen 2004;Tsiklauri et al 2004;Mendoza-Briceño, Sigalotti, and Erdélyi 2005;Mok et al 2008;Antolin, Shibata, and Vissers 1 Most of these observations are done with imaging instruments and thus the speeds correspond to projected values in the plane of the sky. However, since all reports correspond to off-limb observations, the values are close to the total velocities, as confirmed by the spectropolarimetric observations in Antolin and Rouppe van der Voort (2012). 2010; Murawski, Zaqarashvili, and Nakariakov 2011).…”

mentioning

confidence: 99%

On-Disk Coronal Rain

2012

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Small and elongated, cool and dense blob-like structures are being reported with high resolution telescopes in physically different regions throughout the solar atmosphere. Their detection and the understanding of their formation, morphology and thermodynamical characteristics can provide important information on their hosting environment, especially concerning the magnetic field, whose understanding constitutes a major problem in solar physics. An example of such blobs is coronal rain, a phenomenon of thermal nonequilibrium observed in active region loops, which consists of cool and dense chromospheric blobs falling along loop-like paths from coronal heights. So far, only off-limb coronal rain has been observed and few reports on the phenomenon exist. In the present work, several datasets of on-disk Hα observations with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST) are analyzed. A special family of on-disk blobs is selected for each dataset and a statistical analysis is carried out on their dynamics, morphology and temperatures. All characteristics present distributions which are very similar to reported coronal rain statistics. We discuss possible interpretations considering other similar blob-like structures reported so far and show that a coronal rain interpretation is the most likely one. Their chromospheric nature and the projection effects (which eliminate all direct possibility of height estimation) on one side, and their small sizes, fast dynamics, and especially, their faint character (offering low contrast with the background intensity) on the other side, are found as the main causes for the absence until now of the detection of this on-disk coronal rain counterpart.

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Dynamics of solar coronal loops

Cited by 146 publications

References 17 publications

Detection of ultra-long-period oscillations in an EUV filament

Detection of ultra-long-period oscillations in an EUV filament

A model for the formation of the active region corona driven by magnetic flux emergence

On-Disk Coronal Rain

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