The Evershed Flow: Flow Geometry and Its Temporal Evolution

Rimmelé, Thomas; Mariño, José María Solé

doi:10.1086/504794

Cited by 102 publications

(120 citation statements)

References 34 publications

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“…However, there are also upflows that migrate in the opposite direction, towards the quiet Sun, which are located mostly in the outer penumbra. This is consistent with the findings of Sobotka et al (1999) who studied the movements of bright penumbral grains related to the upflow structures (e.g., Rimmele & Marino 2006;Ichimoto et al 2007). The downflow patches also drift in both directions with speeds comparable to those of the upflow regions.…”

Section: Downflows Statisticssupporting

confidence: 92%

“…The upflow velocities in the penumbral bright grains are larger than those reported by Rimmele & Marino (2006, around 1 km s −1 ) and comparable to those reported by Sobotka & Jurčák (2009, between 1-2 km s −1 ), but still smaller than the theoretically predicted 3 km s −1 from the magnetic-flux-tube model by Schlichenmaier et al (1998). The magnetic field strength in the upflow regions is comparable to the values reported by Sobotka & Jurčák (2009) for penumbral bright grains and also to values found for the inner penumbra by e.g., Jurčák et al (2007), Borrero et al (2006), andBellot Rubio et al (2004).…”

Section: Plasma Properties In the Downflow Patchescontrasting

confidence: 57%

“…This relation is dependent on the lifetime of the downflows with maximum of 62% reached for downflows lasting for about 6 min. By assuming that the hot material above the continuum-forming layer created by the upflow is no longer forced to follow the field lines (becoming an horizontal outflow, Rimmele & Marino 2006), it would radiatively cool down and fall back creating a temporal downflow. This explanation is supported by the difference in the continuum intensity within both the upflow regions and the downflow patches, the latter occurring in darker regions.…”

Section: Discussionmentioning

confidence: 99%

“…This can be explained, if we assume that the configuration of the flux tube carrying the flow can be described by the simulations of Schlichenmaier et al (1998) confirmed observationally by Rimmele & Marino (2006). If the flow in the filament were to weaken and the flux tube to collapse, then we would end up with hot material above the continuum formation layer that is no longer forced to follow the field lines of the flux tube.…”

Section: Origin Of the Downflow Patchesmentioning

confidence: 99%

“…With increasing spatial resolution, the fine structure of the flow pattern has been discovered in the past decade. It was found (see e.g., Rimmele & Marino 2006;Ichimoto et al 2007, and references therein) that the Evershed flow starts with the upflow in bright penumbral grains and becomes horizontal within one arcsecond. Westendorp Plaza et al (2001) found a downflow regions in the outer penumbra that have opposite magnetic field polarity than the sunspot umbra and suggested that these might be the sinks of the Evershed flow.…”

Section: Introductionmentioning

confidence: 99%

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Temporal downflows in a penumbra

Jurčák

Katsukawa

2010

A&A

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Aims. We analyze temporal downflow patches that are located in a penumbra and have the same polarity of the magnetic field as a sunspot umbra. Methods. The repetitive 2 wide raster scans of penumbral regions that are taken with one minute cadence by the Hinode spectropolarimeter are used to detect the line-of-sight velocities in the penumbra from enhanced signals in the wings of Stokes V profiles. The lifetimes and positions within penumbra of the identified downflow patches are investigated. The plasma properties of the downflow patches are determined using the inversions of the observed Stokes profiles. Results. The temporal downflows have lifetimes of up to fourteen minutes. Some of them are related to the disappearance or weakening of nearby upflow regions or to the chromospheric brightenings. The downflows take place in regions with stronger and more vertical magnetic fields than the upflow regions.

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Section: Downflows Statisticssupporting

confidence: 92%

Section: Plasma Properties In the Downflow Patchescontrasting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Section: Origin Of the Downflow Patchesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temporal downflows in a penumbra

Jurčák

Katsukawa

2010

A&A

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High‐resolution observations of extremely bright penumbral grains

2008

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We observed a cluster of extremely bright penumbral grains located at the inner limb-side penumbra of the leading sunspot in active region NOAA 10892. The penumbral grains in the cluster showed a typical peak intensity of 1.58 times the intensity I0 of the granulation surrounding the sunspot. The brightest specimen even reached values of 1.8-2.0 I0, thus, exceeding the temperatures of the brightest granules in the immediate surroundings of the sunspot. We find that the observed sample of extremely bright penumbral grains is an intermittent phenomenon, that disappears on time scales of hours. Horizontal flow maps indicating proper motions reveal that the cluster leaves a distinct imprint on the penumbral flow field. We find that the divergence line co-located with the cluster is displaced from the middle penumbra closer towards the umbra and that the radial outflow velocities are significantly increased to speeds in excess of 2 km s −1 . The extremely bright penumbral grains, which are located at the inner limb-side penumbra, are also discernible in offband Hα images down to Hα ± 0.045 nm. We interpret the observations in the context of the moving flux tube model arguing that hotter than normal material is rapidly ascending along the inner footpoint of the embedded flux tube, i.e., the ascending hot material is the cause of the extremely bright penumbral grains. This study is based on speckle-reconstructed broad-band images taken at 600 nm and chromospheric Hα observations obtained with two-dimensional spectroscopy. All data were taken with adaptive optics under very good seeing conditions at the Dunn Solar Telescope, National Solar Observatory/Sacramento Peak, New Mexico on 2006 June 10.

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Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396

et al. 2016

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Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multiinstrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si i λ1082.7 nm line, the chromospheric He i λ1083.0 nm triplet, and the photospheric Ca i λ1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the "Stokes Inversions based on Response functions" (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots.

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The Evershed Flow: Flow Geometry and Its Temporal Evolution

Cited by 102 publications

References 34 publications

Temporal downflows in a penumbra

Temporal downflows in a penumbra

High‐resolution observations of extremely bright penumbral grains

Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396

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