Magnetic tornadoes as energy channels into the solar corona

Wedemeyer, Sven; Scullion, Eamon; Steiner, O.; Voort, L. H. M. Rouppe van der; Rodríguez, J. de la Cruz; Fedun, V.; Erdélyi, R.

doi:10.1038/nature11202

Cited by 307 publications

(415 citation statements)

References 30 publications

Supporting

Mentioning

369

Contrasting

Unclassified

Order By: Relevance

“…Ludwig et al (2006) suggest that the reduced level of horizontal shearing at low Mach number may be the explanation. Vortices are also observed and simulated in the Sun (Wedemeyer-Böhm et al 2012), although they are less prominent in low resolution models.…”

Section: Granulation Propertiesmentioning

confidence: 93%

Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid

Tremblay

Ludwig

Freytag

et al. 2013

A&A

View full text Add to dashboard Cite

Three-dimensional model atmospheres for giants, dwarfs, and white dwarfs, computed with the CO5BOLD code and part of the CIFIST grid, have been used for spectroscopic and asteroseismic studies. Unlike existing plane-parallel 1D structures, these simulations predict the spatially and temporally resolved emergent intensity so that granulation can be analysed, which provides insights on how convective energy transfer operates in stars. The wide range of atmospheric parameters of the CIFIST 3D simulations (3600 < T eff (K) < 13 000 and 1 < log g < 9) allows the comparison of convective processes in significantly different environments. We show that the relative intensity contrast is correlated with both the Mach and Péclet numbers in the photosphere. The horizontal size of granules varies between 3 and 10 times the local pressure scale height, with a tight correlation between the factor and the Mach number of the flow. Given that convective giants, dwarfs, and white dwarfs cover the same range of Mach and Péclet numbers, we conclude that photospheric convection operates in a very similar way in those objects.

show abstract

Section: Granulation Propertiesmentioning

confidence: 93%

Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid

Tremblay

Ludwig

Freytag

et al. 2013

A&A

View full text Add to dashboard Cite

show abstract

“…Either it diffuses into the magnetic features across field lines, which runs counter to the estimates of Hasan & Schüssler (1985), or the lifetimes of BPs, i.e., kilogauss features are rather short, or the plasma with the strong field is continually mixing with relatively field-free plasma in the immediate surroundings of the magnetic elements. This last process may be related to the vortices found in the simulations around magnetic elements by, e.g., Moll et al (2011), and observationally by Bonet et al (2010) and Wedemeyer-Böhm et al (2012).…”

Section: Discussionmentioning

confidence: 99%

Comparison of solar photospheric bright points between Sunrise observations and MHD simulations

Riethmüller

Solanki

Berdyugina

et al. 2014

A&A

View full text Add to dashboard Cite

Bright points (BPs) in the solar photosphere are thought to be the radiative signatures (small-scale brightness enhancements) of magnetic elements described by slender flux tubes or sheets located in the darker intergranular lanes in the solar photosphere. They contribute to the ultraviolet (UV) flux variations over the solar cycle and hence may play a role in influencing the Earth's climate. Here we aim to obtain a better insight into their properties by combining high-resolution UV and spectro-polarimetric observations of BPs by the Sunrise Observatory with 3D compressible radiation magnetohydrodynamical (MHD) simulations. To this end, full spectral line syntheses are performed with the MHD data and a careful degradation is applied to take into account all relevant instrumental effects of the observations. In a first step it is demonstrated that the selected MHD simulations reproduce the measured distributions of intensity at multiple wavelengths, line-of-sight velocity, spectral line width, and polarization degree rather well. The simulated line width also displays the correct mean, but a scatter that is too small. In the second step, the properties of observed BPs are compared with synthetic ones. Again, these are found to match relatively well, except that the observations display a tail of large BPs with strong polarization signals (most likely network elements) not found in the simulations, possibly due to the small size of the simulation box. The higher spatial resolution of the simulations has a significant effect, leading to smaller and more numerous BPs. The observation that most BPs are weakly polarized is explained mainly by the spatial degradation, the stray light contamination, and the temperature sensitivity of the Fe i line at 5250.2 Å. Finally, given that the MHD simulations are highly consistent with the observations, we used the simulations to explore the properties of BPs further. The Stokes V asymmetries increase with the distance to the center of the mean BP in both observations and simulations, consistent with the classical picture of a production of the asymmetry in the canopy. This is the first time that this has been found also in the internetwork. More or less vertical kilogauss magnetic fields are found for 98% of the synthetic BPs underlining that basically every BP is associated with kilogauss fields. At the continuum formation height, the simulated BPs are on average 190 K hotter than the mean quiet Sun, the mean BP field strength is found to be 1750 G, and the mean inclination is 17 • , supporting the physical flux-tube paradigm to describe BPs. On average, the synthetic BPs harbor downflows increasing with depth. The origin of these downflows is not yet understood very well and needs further investigation.

show abstract

“…Throughout the last decade, a number of authors, including Walsh and Ireland (2003), Aschwanden (2005), McIntosh et al (2011), Wedemeyer-Böhm et al (2012, Winebarger et al (2013), demonstrated that one of the several mechanisms, involving small-scale X-ray jets, bright points, micro-and nanoflares as well as Alfvén and MHD turbulence and waves, are able to provide partial explanations for the extreme heating of coronal plasma. Mass and energytransport between the lower atmosphere (photosphere and chromosphere) and the outer atmosphere (corona) is, in general, a challenging concern.…”

Section: Role Of Magnetic Fields In Coronal and Chromospheric Heatingmentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

172

123

View full text Add to dashboard Cite

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

show abstract

Magnetic tornadoes as energy channels into the solar corona

Cited by 307 publications

References 30 publications

Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid

Granulation properties of giants, dwarfs, and white dwarfs from the CIFIST 3D model atmosphere grid

Comparison of solar photospheric bright points between Sunrise observations and MHD simulations

The magnetic field in the solar atmosphere

Contact Info

Product

Resources

About