Are Giant Tornadoes the Legs of Solar Prominences?

Wedemeyer, Sven; Scullion, Eamon; Voort, L. Rouppe van der; Bosnjak, Antonija; Antolin, Patrick

doi:10.1088/0004-637x/774/2/123

Cited by 74 publications

(96 citation statements)

References 79 publications

(112 reference statements)

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“…We looked at the velocity vector map (Fig. 9 left top panel) to detect rotations of the velocity vector related to the feet of the filament or lateral extensions of the filament channel, as suspected in some papers (Wedemeyer et al 2013). We did not find any clear case at the scale of the supergranule.…”

Section: Velocity Vectors and Corks Distribution In The Filament Channelmentioning

confidence: 99%

“…Polar crown filaments also have footpoints feet that appear as dark spots or bushes of threads in good spatial resolution Hα images. Recently, a new name has appeared for the structures connecting prominences with the photosphere, "pillars" when they are observed at the limb (Wedemeyer et al 2013;Schmieder et al 2013c). However, the identification as footpoints feet has not yet been established.…”

Section: Introductionmentioning

confidence: 99%

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Proper horizontal photospheric flows in a filament channel

Schmieder

Roudier

Mein

et al. 2014

A&A

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Context. An extended filament in the central part of the active region NOAA 11106 crossed the central meridian on Sept. 17, 2010 in the southern hemisphere. It has been observed in Hα with the THEMIS telescope in the Canary Islands and in 304 Å with the EUV imager (AIA) onboard the Solar Dynamic Observatory (SDO). Counterstreaming along the Hα threads and bright moving blobs (jets) along the 304 Å filament channel were observed during 10 h before the filament erupted at 17:03 UT. Aims. The aim of the paper is to understand the coupling between magnetic field and convection in filament channels and relate the horizontal photospheric motions to the activity of the filament.Methods. An analysis of the proper photospheric motions using SDO/HMI continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as the large scale photospheric flows, was performed for three hours. Using corks, we derived the passive scalar points and produced a map of the cork distribution in the filament channel. Averaging the velocity vectors in the southern hemisphere in each latitude in steps of 3.5 arcsec, we defined a profile of the differential rotation. Results. Supergranules are clearly identified in the filament channel. Diverging flows inside the supergranules are similar in and out of the filament channel. Converging flows corresponding to the accumulation of corks are identified well around the Hα filament feet and at the edges of the EUV filament channel. At these convergence points, the horizontal photospheric velocity may reach 1 km s −1 , but with a mean velocity of 0.35 km s −1 . In some locations, horizontal flows crossing the channel are detected, indicating eventually large scale vorticity. Conclusions. The coupling between convection and magnetic field in the photosphere is relatively strong. The filament experienced the convection motions through its anchorage points with the photosphere, which are magnetized areas (ends, feet, lateral extensions of the EUV filament channel). From a large scale point-of-view, the differential rotation induced a shear of 0.1 km s −1 in the filament. From a small scale point-of-view, any convective motions favored the interaction of the parasitic polarities responsible for the anchorages of the filament to the photosphere with the surrounding network and may explain the activity of the filament.

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Section: Velocity Vectors and Corks Distribution In The Filament Channelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Proper horizontal photospheric flows in a filament channel

Schmieder

Roudier

Mein

et al. 2014

A&A

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“…This work aims to provide an insight into the physical conditions found in the so-called large-scale solar tornadoes that have been observed in the legs of prominences (Wedemeyer et al 2013). There is an ongoing debate about how to interpret the apparent rotation of these features (see Orozco Suárez et al 2012;Li et al 2012;Su et al 2012Su et al , 2014Panesar et al 2013).…”

Section: Introductionmentioning

confidence: 99%

A solar tornado observed by EIS

Levens

Labrosse

Fletcher

et al. 2015

A&A

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Context. The term "solar tornadoes" has been used to describe apparently rotating magnetic structures above the solar limb, as seen in high resolution images and movies from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). These often form part of the larger magnetic structure of a prominence, however the links between them remain unclear. Here we present plasma diagnostics on a tornado-like structure and its surroundings, seen above the limb by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard the Hinode satellite. Aims. We aim to extend our view of the velocity patterns seen in tornado-like structures with EIS to a wider range of temperatures and to use density diagnostics, non-thermal line widths, and differential emission measures to provide insight into the physical characteristics of the plasma. Methods. Using Gaussian fitting to fit and de-blend the spectral lines seen by EIS, we calculated line-of-sight velocities and nonthermal line widths. Along with information from the CHIANTI database, we used line intensity ratios to calculate electron densities at each pixel. Using a regularised inversion code we also calculated the differential emission measure (DEM) at different locations in the prominence. Results. The split Doppler-shift pattern is found to be visible down to a temperature of around log T = 6.0. At temperatures lower than this, the pattern is unclear in this data set. We obtain an electron density of log n e = 8.5 when looking towards the centre of the tornado structure at a plasma temperature of log T = 6.2, as compared to the surroundings of the tornado structure where we find log n e to be nearer 9. Non-thermal line widths show broader profiles at the tornado location when compared to the surrounding corona. We discuss the differential emission measure in both the tornado and the prominence body, which suggests that there is more contribution in the tornado at temperatures below log T = 6.0 than in the prominence.

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“…Orozco Suárez et al (2012) found opposite Doppler shifts at the edge of a prominence foot and interpreted these shifts as prominence plasma that rotates around the axis. Recently, Wedemeyer et al (2013) and Su et al (2014) separately found redshifted and blueshifted regions on A&A 570, A93 (2014) the two sides of the prominence leg and proposed that there is rotational motion in a tornado-like prominence. All these observations together show that spinning and twisting motions are common on the Sun.…”

Section: Introductionmentioning

confidence: 99%

Conversion from mutual helicity to self-helicity observed with IRIS

Peter

Chen

et al. 2014

A&A

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Context. In the upper atmosphere of the Sun observations show convincing evidence for crossing and twisted structures, which are interpreted as mutual helicity and self-helicity. Aims. We use observations with the new Interface Region Imaging Spectrograph (IRIS) to show the conversion of mutual helicity into self-helicity in coronal structures on the Sun. Methods. Using far UV spectra and slit-jaw images from IRIS and coronal images and magnetograms from SDO, we investigated the evolution of two crossing loops in an active region, in particular, the properties of the Si IV line profile in cool loops. Results. In the early stage two cool loops cross each other and accordingly have mutual helicity. The Doppler shifts in the loops indicate that they wind around each other. As a consequence, near the crossing point of the loops (interchange) reconnection sets in, which heats the plasma. This is consistent with the observed increase of the line width and of the appearance of the loops at higher temperatures. After this interaction, the two new loops run in parallel, and in one of them shows a clear spectral tilt of the Si IV line profile. This is indicative of a helical (twisting) motion, which is the same as to say that the loop has self-helicity. Conclusions. The high spatial and spectral resolution of IRIS allowed us to see the conversion of mutual helicity to self-helicity in the (interchange) reconnection of two loops. This is observational evidence for earlier theoretical speculations.

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Are Giant Tornadoes the Legs of Solar Prominences?

Cited by 74 publications

References 79 publications

Proper horizontal photospheric flows in a filament channel

Proper horizontal photospheric flows in a filament channel

A solar tornado observed by EIS

Conversion from mutual helicity to self-helicity observed with IRIS

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