Dynamics of solar coronal loops

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

doi:10.1051/0004-6361:20031328

Cited by 161 publications

(198 citation statements)

References 27 publications

Supporting

Mentioning

176

Contrasting

Order By: Relevance

“…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: 73%

“…While now time-dependent models including plasma flows are widely used, they mostly concentrate on the loop evolution in a magnetic field that changes only slightly or not at all (see, e.g., review by Reale 2010). This applies to 1D models for the dynamic evolution of loops, for example, accounting for siphon flows (Boris & Mariska 1982), in response to intermittent nanoflare heating (Hansteen 1993), or concerning catastrophic cooling (Müller et al 2003). In addition, 3D models of the coronal loop structure considered either a constant or slowly changing magnetic field in the photosphere (Gudiksen & Nordlund 2002;Bingert & Peter 2011;Lionello et al 2013).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Chen

Peter

Bingert

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Cooling Phasementioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

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

Chen

Peter

Bingert

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The heat conductivity according to Spitzer [23], q ∝ T 5/2 ∇T, is very sensitive to the temperature T. Known at least since the first one-dimensional coronal models including the transition region [24][25][26], as a consequence of the heat conductivity in the transition region the temperature gradient becomes very steep, which requires a very small grid spacing. In more recent models, the grid spacing is as small as 1 km [27] or even smaller when an adaptive grid is used [28,29]. As pointed out early in [30,31], other (turbulence) processes might take over well before such small scales for the temperature gradients are reached.…”

Section: Introductionmentioning

confidence: 99%

What can large-scale magnetohydrodynamic numerical experiments tell us about coronal heating?

Peter

2015

Phil. Trans. R. Soc. A.

Self Cite

View full text Add to dashboard Cite

The upper atmosphere of the Sun is governed by the complex structure of the magnetic field. This controls the heating of the coronal plasma to over a million kelvin. Numerical experiments in the form of threedimensional magnetohydrodynamic simulations are used to investigate the intimate interaction between magnetic field and plasma. These models allow one to synthesize the coronal emission just as it would be observed by real solar instrumentation. Largescale models encompassing a whole active region form evolving coronal loops with properties similar to those seen in extreme ultraviolet light from the Sun, and reproduce a number of average observed quantities. This suggests that the spatial and temporal distributions of the heating as well as the energy distribution of individual heat deposition events in the model are a good representation of the real Sun. This provides evidence that the braiding of fieldlines through magneto-convective motions in the photosphere is a good concept to heat the upper atmosphere of the Sun.

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Dynamics of solar coronal loops

Cited by 161 publications

References 27 publications

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

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

What can large-scale magnetohydrodynamic numerical experiments tell us about coronal heating?

On-Disk Coronal Rain

Contact Info

Product

Resources

About