CRISP Spectropolarimetric Imaging of Penumbral Fine Structure

Scharmer, G.; Narayan, G.; Hillberg, T.; Rodríguez, J. de la Cruz; Löfdahl, Mats G.; Kiselman, Dan; Sütterlin, P.; Noort, M. van; Lagg, A.

doi:10.1086/595744

Cited by 416 publications

(395 citation statements)

References 17 publications

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“…Rouppe van der Voort et al, 2009;Sekse, Rouppe van der Voort, and De Pontieu, 2012;Pereira et al, 2014) that the RBEs observed in profiles of different chromospheric lines are on-disk counter parts of solar spicules. In addition, it is also reported that the doppler velocity of RBEs increases along their length in CHs when observed in the 8542Å (Ca II) spectral line using the CRisp Imaging SpectroPolarimeter instrument (CRISP, Scharmer et al (2008)) at the Swedish 1-m Solar Telescope (SST). However, no such trend was observed for QS RBEs (see Sekse et al, 2013 for detailed discussion).…”

Section: Resultsmentioning

confidence: 99%

Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions

et al. 2016

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Recent IRIS observations have revealed a prevalence of intermittent small-scale jets with apparent speeds of 80 -250 km s −1 , emanating from smallscale bright regions inside network boundaries of coronal holes. We find that these network jets appear not only in coronal holes but also in quiet-sun regions. Using IRIS 1330Å (C II) slit-jaw images, we extract several parameters of these network jets, e.g. apparent speed, length, lifetime and increase in foot-point brightness. Using several observations, we find that some properties of the jets are very similar but others are obviously different between the quiet sun and coronal holes. For example, our study shows that the coronal-hole jets appear to be faster and longer than those in the quiet sun. This can be directly attributed to a difference in the magnetic configuration of the two regions with open magnetic field lines rooted in coronal holes and magnetic loops often present in quiet sun. We have also detected compact bright loops, likely transition region loops, mostly in quiet sun. These small loop-like regions are generally devoid of network jets. In spite of different magnetic structures in the coronal hole and quiet sun in the transition region, there appears to be no substantial difference for the increase in foot-point brightness of the jets, which suggests that the generation mechanism of these network jets is likely the same in both regions.

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Section: Resultsmentioning

confidence: 99%

Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions

et al. 2016

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“…On one hand, Schrijver (2001), using various channels of TRACE, has estimated the occurrence rate of coronal rain in active region loops to be at most once every two days, suggesting a sporadic character for the phenomenon. On the other hand, in Hα observations at the limb with the CRisp Imaging SpectroPolarimeter (CRISP, Scharmer et al 2008), at the Swedish 1-m Solar Telescope (SST, Scharmer et al 2003a), Antolin and Rouppe van der Voort (2012) present a ubiquitous character of coronal rain, and show that it is composed of a myriad of small blobs, with sizes that are, on average, 300 km in width and 700 km in length. Furthermore, if close enough together and in large enough quantities, the blobs are seen as large clumps termed 'showers'.…”

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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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“…We obtained a series of observations at the Swedish 1 m Solar Telescope (SST; Scharmer et al 2003) on La Palma using the Crisp Imaging SpectroPolarimeter (CRISP; Scharmer et al 2008) instrument. CRISP is a dual Fabry-Pérot interferometer (FPI) that contains three high-speed CCD cameras (35 frames s −1 with an exposure time of 17 ms per frame): two cameras behind the FPI and a polarizing beam splitter, and a third "wide band" camera located before the FPI, which is used as an anchor channel for image processing.…”

Section: Observationsmentioning

confidence: 99%

THE APPEARANCE OF SPICULES IN HIGH RESOLUTION OBSERVATIONS OF Ca ii H AND Hα

Pereira

Voort

Carlsson

2016

ApJ

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Solar spicules are chromospheric fibrils that appear everywhere on the Sun, yet their origin is not understood. Using high resolution observations of spicules obtained with the Swedish 1 m Solar Telescope, we aim to understand how spicules appear in filtergrams and Dopplergrams, how they compare in Ca II H and Hα filtergrams, and what can make them appear and disappear. We find that spicules display a rich and detailed spatial structure, and show a distribution of transverse velocities that, when aligned with the line of sight, can make them appear at different Hα wing positions. They become more abundant at positions closer to the line core, reflecting a distribution of Doppler shifts and widths. In Hα width maps they stand out as bright features both on disk and off limb, reflecting their large Doppler motions and possibly higher temperatures than in the typical Hα formation region. Spicule lifetimes measured from narrowband images at only a few positions will be an underestimate because Doppler shifts can make them disappear prematurely from such images; for such cases, width maps are a more robust tool. In Hα and Ca II H filtergrams, off-limb spicules essentially have the same properties, appearance, and evolution. We find that the sudden appearance of spicules can be explained by Doppler shifts from their transverse motions, and does not require other convoluted explanations.

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CRISP Spectropolarimetric Imaging of Penumbral Fine Structure

Cited by 416 publications

References 17 publications

Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions

Statistical Study of Network Jets Observed in the Solar Transition Region: a Comparison Between Coronal Holes and Quiet-Sun Regions

On-Disk Coronal Rain

THE APPEARANCE OF SPICULES IN HIGH RESOLUTION OBSERVATIONS OF Ca ii H AND Hα

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