High-Resolution Observations of Siphon Flows in a Solar Magnetic Pore

Guglielmino, Salvo L.; Zuccarello, F.

doi:10.1088/2041-8205/743/1/l9

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…Nonetheless, as suggested by Cargill & Priest (1980), an oppositely directed flow may occur in a fibril with an established siphon flow as a result of a change in pressure difference. Evidence for the existence of such a counterflow has for instance been provided by Guglielmino & Zuccarello (2011), in a recent study of a pore and its surroundings.…”

Section: Driving Mechanismmentioning

confidence: 95%

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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Section: Driving Mechanismmentioning

confidence: 95%

Flocculent Flows in the Chromospheric Canopy of a Sunspot

Vissers

Voort

2012

ApJ

111

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“…Related to the magnetic connectivity is the question of the physical driver of both the regular and inverse Evershed effect. Magnetic field lines that connect sites of significantly different magnetic field strength can lead to directed mass flows from the weaker to the stronger foot point ("siphon flows"; Meyer & Schmidt 1968). Siphon flows have been invoked for both the upper solar atmosphere (Cargill & Priest 1980;Noci 1981;Lagg et al 2007) and the photosphere (Thomas 1988;Guglielmino & Zuccarello 2011), and also for the regular Evershed effect Montesinos & Thomas 1997;Schlichenmaier et al 1998a,b). One peculiarity of fast siphon flows is the generation of a (standing) shock in the down-flow branch (Thomas & Montesinos 1991).…”

Section: Introductionmentioning

confidence: 99%

A Three-Dimensional View of the Thermal Structure in a Super-Penumbral Canopy

Beck¹,

Choudhary²,

Rezaei³

2014

ApJ

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We investigate the thermal topology in a super-penumbral canopy by determining the threedimensional (3D) thermal structure of an active region. We derive the temperature stratifications in the active region by an inversion of the Ca ii IR line at 854.2 nm, assuming local thermal equilibrium (LTE). We trace the 3D topology of individual features located in the super-penumbral canopy, mainly radially oriented fibrils. We find that about half of the fibrils form short, arched, low-lying loops in the temperature cube. These closed loops connect from bright grains that are either in or close to the penumbra to the photosphere a few Mms away from the sunspot. They reach less than 1 Mm in height. The other half of the fibrils rise with distance from the sunspot until they leave the Ca ii IR formation height. Many of the fibrils show a central dark core and two lateral brightenings as seen in line-core intensity images. The corresponding velocity image shows fibrils that are as wide as the fibrils seen in intensity without a lateral substructure. Additionally, we study one example of exceptional brightness in more detail. It belongs to a different class of structures without prominent mass flows and with a 3D topology formed by two parallel, closed loops connecting patches of opposite polarity. We present evidence that the inverse Evershed flow into the sunspot in the lower chromosphere is the consequence of siphon flows along short loops that connect photospheric foot points. The dark-cored structure of the chromospheric fibrils cannot have an convective origin because of their location above regular granulation in an optically thin atmosphere. The dark core most likely results from an opacity difference between the central axis and the lateral edges caused by the significant flow speed along the fibrils.

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“…It has the characteristics of being supersonic (e.g., Teriaca et al 2004;Bethge et al 2012 and references therein) and it may be the signature of a localized heating event at one footpoint. In this context, we recall that Guglielmino & Zuccarello (2011) found a countersiphon flow at the edge of a pore in the photosphere. A small-sized (~6000 km) arch-shaped structure had a 4 km s…”

Section: à3mentioning

confidence: 86%

Solar activity and its evolution across the corona: recent advances

Zuccarello¹,

Balmaceda

Cessateur

et al. 2013

J. Space Weather Space Clim.

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Solar magnetism is responsible for the several active phenomena that occur in the solar atmosphere. The consequences of these phenomena on the solar-terrestrial environment and on Space Weather are nowadays clearly recognized, even if not yet fully understood. In order to shed light on the mechanisms that are at the basis of the Space Weather, it is necessary to investigate the sequence of phenomena starting in the solar atmosphere and developing across the outer layers of the Sun and along the path from the Sun to the Earth. This goal can be reached by a combined multi-disciplinary, multi-instrument, multi-wavelength study of these phenomena, starting with the very first manifestation of solar active region formation and evolution, followed by explosive phenomena (i.e., flares, erupting prominences, coronal mass ejections), and ending with the interaction of plasma magnetized clouds expelled from the Sun with the interplanetary magnetic field and medium. This wide field of research constitutes one of the main aims of COST Action ES0803: Developing Space Weather products and services in Europe. In particular, one of the tasks of this COST Action was to investigate the Progress in Scientific Understanding of Space Weather. In this paper we review the state of the art of our comprehension of some phenomena that, in the scenario outlined above, might have a role on Space Weather, focusing on the researches, thematic reviews, and main results obtained during the COST Action ES0803.

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High-Resolution Observations of Siphon Flows in a Solar Magnetic Pore

Cited by 5 publications

References 25 publications

Flocculent Flows in the Chromospheric Canopy of a Sunspot

Flocculent Flows in the Chromospheric Canopy of a Sunspot

A Three-Dimensional View of the Thermal Structure in a Super-Penumbral Canopy

Solar activity and its evolution across the corona: recent advances

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