Fast events and waves in an active region of the Sun observed in H$\mathsf{\alpha}$ with high spatial resolution

Nuño, B. Sánchez-Andrade; González, N. Bello; Rodríguez, J. Blanco; Kneer, F.; Puschmann, K. G.

doi:10.1051/0004-6361:20079231

Cited by 13 publications

(11 citation statements)

References 36 publications

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“…One sees that large-scale structures (>10 ) dominate the intensity and flow patterns in most of the Hα images. These deserve a separate investigation, such as that of magneto-dynamic waves and jets discussed in Sánchez-Andrade Nuño et al (2008). We concentrate here on the broadband and Hα wing intensities for the present study of EBs at small scales.…”

Section: Discussionmentioning

confidence: 99%

On the structure and dynamics of Ellerman bombs

González

Danilović

Kneer³

2013

A&A

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Aims. We study the structure and dynamics of three Ellerman bombs (EBs) observed in an evolving active region. Methods. The active region NOAA 11271 was observed with the Vacuum Tower Telescope at Observatorio del Teide/Tenerife on August 18, 2011. We used the two-dimensional Triple Etalon SOlar Spectrometer (TESOS) to obtain time sequences of the active region and of EBs in Hα at a cadence of 15 s. Simultaneously, we obtained full Stokes profiles with the Tenerife Infrared Polarimeter (TIP II) in the two magnetically sensitive Fe i infrared lines (IR) at 1.56 μ, scanning spatial sections of the area with cadences of 28−46 s. The Hα data were reconstructed with speckle methods to study the evolution of the atmospheric stratification. Two methods were used to extract magnetic field information from the IR Stokes profiles: 1) fitting of the (Q, U, V) profiles by Gaussians; and 2) applying the Milne-Eddington approximation, assuming two separate magnetic structures in the resolution element and fitting by trial and error some profiles from the EB areas. Data from SDO-HMI and -AIA were also used. We performed two-dimensional (2D) non-LTE radiative transfer calculations of Hα in parameterised models of EBs. Results. The three EBs studied in detail occurred in a complex active region near sunspots. They were very bright with a factor of 1.5-2.8 brighter than the nearby area. They lived for 1/2 h and longer. They were related to broadband faculae, but the latter were not the brightest features in the field of view. The EBs occurred in magnetic field configurations with opposite polarity close together. One EB was located at the outskirts of a penumbra of a complex sunspot and showed repeated "flaring" in SDO-AIA data. Another was close to a strong field patch and moved into this during the end of its lifetime. The third EB showed clear changes of field structure during the time it was observed. We obtained from the 2D modelling that heating and increase in Hα opacity are likely to occur at heights of 300-800 km. Line shifts and asymmetries can well be reproduced by velocities at these heights and also at much larger heights. Conclusions. The three EBs occurred at sites with magnetic fields of opposite polarity, which were likely the cause of the Hα brightening upon reconnection.

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Section: Discussionmentioning

confidence: 99%

On the structure and dynamics of Ellerman bombs

González

Danilović

Kneer³

2013

A&A

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“…Features with similar morphology and behavior have also been found in other studies, albeit propagating at lower velocities. For instance, Sánchez-Andrade Nuño et al (2008) found chromospheric magneto-acoustic waves in Hα observations. These waves manifest themselves mainly as (trains of) blobs with average dimensions as small as 725 km (1 arcsec) in length and 360 km (0.5 arcsec) in width, propagating at phase velocities between 12-42 km s −1 .…”

Section: Driving Mechanismmentioning

confidence: 99%

Flocculent Flows in the Chromospheric Canopy of a Sunspot

Vissers

Voort

2012

ApJ

111

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High-quality imaging spectroscopy in the Hα line, obtained with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST) at La Palma and covering a small sunspot and its surroundings, are studied. They exhibit ubiquitous flows both along fibrils making up the chromospheric canopy away from the spot and in the superpenumbra. We term these flows "flocculent" to describe their intermittent character, that is morphologically reminiscent of coronal rain. The flocculent flows are investigated further in order to determine their dynamic and morphological properties. For the measurement of their characteristic velocities, accelerations and sizes, we employ a new versatile analysis tool, the CRisp SPectral EXplorer (CRISPEX), which we describe in detail. Absolute velocities on the order of 7.2-82.4 km s −1 are found, with an average value of 36.5±5.9 km s −1 and slightly higher typical velocities for features moving towards the sunspot than away. These velocities are much higher than those determined from the shift of the line core, which shows patches around the sunspot with velocity enhancements of up to 10-15 km s −1 (both red-and blueshifted). Accelerations are determined for a subsample of features, that show clear accelerating or decelerating behavior, yielding an average of 270±63 m s −2 and 149±63 m s −2 for accelerating and decelerating features, respectively. Typical flocculent features measure 627±44 km in length and 304±30 km in width. On average 68 features are detected per minute, with an average lifetime of 67.7±8.8 s. The dynamics and phenomenology of the flocculent flows suggest they may be driven by a siphon flow, where the flocculence could arise from a density perturbation close to one of the footpoints or along the loop structure.

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“…The information content of high-resolution imaging data was extended to high-resolution imaging spectroscopy with the Interferometric BIdimensional Spectrometer (IBIS; Cavallini 2006;Reardon and Cavallini 2008) at the DST, the GREGOR Fabry-Pérot Interferometer (GFPI; Puschmann et al 2006Puschmann et al , 2007Puschmann et al , 2012aPuschmann et al ,b,c, 2013 at the German Vacuum Tower Telescope (VTT; Tenerife, Spain; Schröter, Soltau, and Wiehr 1985), or the CRISP instrument (Scharmer et al 2008) at the Swedish 1-m Solar Telescope (SST; La Palma, Spain). Such data of high spatial resolution in Hα and the Ca ii IR line at 854 nm have been used to determine the properties of spicules or related features off the limb (Pasachoff, Jacobson, and Sterling 2009;De Pontieu et al 2012) or on the solar disc (Langangen et al 2008;Sánchez-Andrade Nuño et al 2008;Rouppe van der Voort et al 2009;Sekse, Rouppe van der Voort, and De Pontieu 2013).…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy at the Solar Limb: II. Are Spicules Heated to Coronal Temperatures?

Beck

Rezaei

Puschmann³

et al. 2016

Sol Phys

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Spicules of the so-called type II were suggested to be relevant for coronal heating because of their ubiquity on the solar surface and their eventual extension into the corona. We investigate whether solar spicules are heated to transition-region or coronal temperatures and reach coronal heights (≫ 6 Mm) using multi-wavelength observations of limb spicules in different chromospheric spectral lines (Ca ii H, Hǫ, Hα, Ca ii IR at 854.2 nm, He i at 1083 nm) taken with slit-spectrographs and imaging spectrometers. We determine the line width of spectrally resolved line profiles in individual spicules and throughout the field of view and estimate the maximal height that different types of off-limb features reach. We derive estimates of the kinetic temperature and the non-thermal velocity from the line width of spectral lines from different chemical elements. We find that most regular -i.e., thin and elongated -spicules reach a maximal height of about 6 Mm above the solar limb. The majority of features found at larger heights are irregularly shaped with a significantly larger lateral extension -of up to a few Mm -than spicules. Both individual and average line profiles in all spectral lines show a decrease in their line width with height above the limb with very few exceptions. Both the kinetic temperature and the non-thermal velocity decrease with height above the limb. We find no indications that the spicules in our data reach coronal heights or transition-region or coronal temperatures.

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Fast events and waves in an active region of the Sun observed in H$\mathsf{\alpha}$ with high spatial resolution

Cited by 13 publications

References 36 publications

On the structure and dynamics of Ellerman bombs

On the structure and dynamics of Ellerman bombs

Flocculent Flows in the Chromospheric Canopy of a Sunspot

Spectroscopy at the Solar Limb: II. Are Spicules Heated to Coronal Temperatures?

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