Observation of a Non-Radial Penumbra in a Flux Emerging Region Under Chromospheric Canopy Fields

Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip R.; Cho, Kyung-Suk

doi:10.1088/2041-8205/769/1/l18

Cited by 30 publications

(30 citation statements)

References 15 publications

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“…This is also supported by the studies of Lim et al (2013) and Zuccarello et al (2014), who found no changes in the structure of chromospheric magnetic fields during the formation of orphan penumbrae.…”

Section: Discussionsupporting

confidence: 75%

Orphan penumbrae: Submerging horizontal fields

Jurčák

Rubio

Sobotka

2014

A&A

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Aims. We investigate the properties of orphan penumbrae, which are photospheric filamentary structures observed in active regions near polarity inversion lines that resemble the penumbra of regular sunspots but are not connected to any umbra. Methods. We use Hinode data from the Solar Optical Telescope to determine the properties of orphan penumbrae. Spectropolarimetric data are employed to obtain the vector magnetic field and line-of-sight velocities in the photosphere. Magnetograms are used to study the overall evolution of these structures, and G-band and Ca ii H filtergrams are to investigate their brightness and apparent horizontal motions.Results. Orphan penumbrae form between regions of opposite polarity in places with horizontal magnetic fields. Their magnetic configuration is that of Ω-shaped flux ropes. In the two cases studied here, the opposite-polarity regions approach each other with time and the whole structure submerges as the penumbral filaments disappear. Orphan penumbrae are very similar to regular penumbrae, including the existence of strong gas flows. Therefore, they could have a similar origin. The main difference between them is the absence of a "background" magnetic field in orphan penumbrae. This could explain most of the observed differences. Conclusions. The fast flows we detect in orphan penumbrae may be caused by the siphon flow mechanism. Based on the similarities between orphan and regular penumbrae, we propose that the Evershed flow is also a manifestation of siphon flows.

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Section: Discussionsupporting

confidence: 75%

Orphan penumbrae: Submerging horizontal fields

Jurčák

Rubio

Sobotka

2014

A&A

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“…The data also clearly showed that the flare related increase of the magnetic field intensity occurred due to both reconfiguring of coronal magnetic fields (i.e., formation of a PEA rooted in the umbra) and emergence of a new flux. We note that there were other locations where photospheric field changed, such as the appearance of a "orphan" penumbra (Strous & Zwaan 1999;Cheung et al 2008;Yurchyshyn et al 2012;Kuckein et al 2012;Lim et al 2013) developed under a stable chromospheric filament, although it is not obvious that these changes either led to or were caused by the flare.…”

Section: Discussionmentioning

confidence: 84%

“…An irregular granulation pattern first appeared there at the flare onset and then developed into an extended system of elongated granules and short penumbra-like filaments (called "orphan" penumbra, arrow in panel f). This pattern is known to be associated with low lying horizontal fields and may indicate the presence of either Ω or U-shaped fields (Strous & Zwaan 1999;Cheung et al 2008;Yurchyshyn et al 2012;Kuckein et al 2012;Lim et al 2013). However, this penumbra like pattern was only associated with positive polarity fields, which according to Figures 7 and 8 appeared to be under a chromospheric filament, FL, that remained undisturbed throughout the flare.…”

Section: Evolution Of the Photospheric Fieldsmentioning

confidence: 98%

Multiwavelength Observations of a Slow-Rise, Multistep X1.6 Flare and the Associated Eruption

Yurchyshyn

Kumar

Cho

et al. 2015

ApJ

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Using multi-wavelength observations we studied a slow rise, multi-step X1.6 flare that began on November 7, 2014 as a localized eruption of core fields inside a δ-sunspot and later engulfed the entire active region. This flare event was associated with formation of two systems of post eruption arcades and several J-shaped flare ribbons showing extremely fine details, irreversible changes in the photospheric magnetic fields, and it was accompanied by a fast and wide coronal mass ejection. Data from the Solar Dynamics Observatory, IRIS spacecraft along with the ground based data from the New Solar Telescope (NST) present evidence that i) the flare and the eruption were directly triggered by a flux emergence that occurred inside a δ-sunspot at the boundary between two umbrae; ii) this event represented an example of the formation of an unstable flux rope observed only in hot AIA channels (131 and 94Å) and LASCO C2 coronagraph images; iii) the global post eruption arcade spanned the entire AR and was due to global scale reconnection occurring at heights of about one solar radii, indicating on the global spatial and temporal scale of the eruption.

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“…1 Observations of orphan penumbrae (Zirin & Wang 1991;Kuckein et al 2012;Lim et al 2013;Jurčák et al 2014b;Zuccarello et al 2014) show that they are comparable in all aspects to regular sunspot penumbrae. These observations prove that sufficient magnetic flux is not a necessary condition for a penumbra formation.…”

Section: Introductionmentioning

confidence: 96%

A distinct magnetic property of the inner penumbral boundary

Jurčák

González

Schlichenmaier

et al. 2016

A&A

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Context. We recently presented evidence that stable umbra-penumbra boundaries are characterised by a distinct canonical value of the vertical component of the magnetic field, B stable ver . In order to trigger the formation of a penumbra, large inclinations in the magnetic field are necessary. In sunspots, the penumbra develops and establishes by colonising both umbral areas and granulation, that is, penumbral magneto-convection takes over in umbral regions with B ver < B stable ver , as well as in granular convective areas. Eventually, a stable umbra-penumbra boundary settles at B stable ver . Aims. Here, we aim to study the development of a penumbra initiated at the boundary of a pore, where the penumbra colonises the entire pore ultimately. Methods. We have used Hinode/SOT G-band images to study the evolution of the penumbra. Hinode/SOT spectropolarimetric data were used to infer the magnetic field properties in the studied region. Results. The penumbra forms at the boundary of a pore located close to the polarity inversion line of NOAA 10960. As the penumbral bright grains protrude into the pore, the magnetic flux in the forming penumbra increases at the expense of the pore magnetic flux. Consequently, the pore disappears completely giving rise to an orphan penumbra. At all times, the vertical component of the magnetic field in the pore is smaller than B stable ver ≈ 1.8 kG. Conclusions. Our findings are in an agreement with the need of B stable ver for establishing a stable umbra-penumbra boundary: while B ver in the pore is smaller than B stable ver , the protrusion of penumbral grains into the pore area is not blocked, a stable pore-penumbra boundary does not establish, and the pore is fully overtaken by the penumbral magneto-convective mode. This scenario could also be one of the mechanisms giving rise to orphan penumbrae.

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Observation of a Non-Radial Penumbra in a Flux Emerging Region Under Chromospheric Canopy Fields

Cited by 30 publications

References 15 publications

Orphan penumbrae: Submerging horizontal fields

Orphan penumbrae: Submerging horizontal fields

Multiwavelength Observations of a Slow-Rise, Multistep X1.6 Flare and the Associated Eruption

A distinct magnetic property of the inner penumbral boundary

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