Magnetic Properties and Flow Angle of the Inverse Evershed Flow at Its Downflow Points

Beck, C.; Choudhary, Debi Prasad

doi:10.3847/1538-4357/ab06f9

Cited by 17 publications

(25 citation statements)

References 63 publications

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“…Photospheric CEFs should not be confused with the more commonly reported chromospheric inverse Evershed flows (St. John 1911b,a;Maltby 1975;Choudhary & Beck 2018; e-mail: castellanos@mps.mpg.de 1 In this paper the radial direction is taken to be parallel to the solar surface and ascribed from the umbra-penumbra boundary, across the penumbra, toward the quiet-Sun. Choudhary 2019). Inverse Evershed flows transport material in the chromospheric penumbrae toward the umbra and are thought to be driven by pressure gradients (siphon flows; e.g., Thomas 1988).…”

Section: Introductionmentioning

confidence: 99%

How rare are counter Evershed flows?

Durán

Lagg

Solanki

2021

A&A

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One of the main characteristics of sunspot penumbrae is the radially outward-directed Evershed flow. Only recently have penumbral regions been reported with similar characteristics to normal penumbral filaments but with an opposite direction of the flow. Such flows directed toward the umbra are known as counter Evershed flows (CEFs). We aim to determine the occurrence frequency of CEFs in active regions (ARs) and to characterize their lifetime and the prevailing conditions in the ARs. We analyzed the continuum images, Dopplergrams, and magnetograms recorded by SDO/HMI of 97 ARs that appeared from 2011 to 2017. We followed the ARs for 9.6 ± 1.4 days on average. We found 384 CEFs in total, with a median value of six CEFs per AR. Counter Evershed flows are a rather common feature, occurring in 83.5% of all ARs regardless of the magnetic complexity of the AR. However, CEFs were only observed, on average, during 5.9% of the mean total duration of all the observations analyzed here. The lifetime of CEFs follows a log-normal distribution with a median value of 10.6−6.0+12.4 h. In addition, we report two populations of CEFs, those that are associated with light bridges and those that are not. We explain that the rarity of reports of CEFs in the literature is a result of highly incomplete coverage of ARs with spectropolarimetric data. By using the continuous observations now routinely available from space, we are able to overcome this limitation.

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Section: Introductionmentioning

confidence: 99%

How rare are counter Evershed flows?

Durán

Lagg

Solanki

2021

A&A

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“…6.4. Relation to Global Sunspot Structure Figure 19 attempts to put our results on the IEF structure and evolution from Choudhary & Beck (2018), Beck & Choudhary (2019) and the current study into the larger picture of sunspot topology and dynamics.…”

Section: Ief Channels and Velocity Packetsmentioning

confidence: 92%

“…In Paper I and Beck & Choudhary (2019) we were only able to track 100 manually identified IEF channels in observations at a low cadence of about 20 min. The current IBIS time series allows us to increase the statistics on the locations of IEF channels and downflow points to more than 10,000.…”

Section: Locations Of Ief Channelsmentioning

confidence: 99%

“…From Hα filtergrams it was found earlier that the the IEF channels contain compression shocks, last for about 70 minutes to more than two hours, and that in many cases old channels are replaced by new ones (Maltby 1975(Maltby , 1997. The flow channels are inclined to the local vertical in the range of 30 • to 80 • (Haugen 1969;Beck & Choudhary 2019). Comprehensive studies of the temporal evolution of both EF and IEF have been carried out using observations with the Universal Birefringent Filter at the Dunn Solar Telescope in the photospheric Fe i line at 557.6 nm and the chromospheric Hα line .…”

Section: Introductionmentioning

confidence: 99%

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Temporal Evolution of the Inverse Evershed Flow

Beck

Choudhary

2020

ApJ

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The inverse Evershed flow (IEF) is an inflow of material into the penumbra of sunspots in the solar chromosphere that occurs along dark, elongated superpenumbral fibrils extending from about the outer edge of the moat cell to the sunspot. The IEF channels exhibit brightenings in the penumbra, where the supersonic IEF descends to the photosphere causing shock fronts with localized heating. We used an 1-hr time-series of spectroscopic observations of the chromospheric spectral lines of Ca ii IR at 854 nm and Hα at 656 nm taken with the Interferometric BIdimensional Spectrometer at the Dunn Solar Telescope to investigate the temporal evolution of IEF channels. Complementary information on the photospheric magnetic field was obtained from observations with the Facility InfraRed Spectropolarimeter at 1083 nm and the Helioseismic and Magnetic Imager. We find that individual IEF channels are long-lived (10-60 min) and only show minor changes in position and flow speed during their life time. Initiation and termination of IEF channels takes several minutes. The IEF channels with line-of-sight velocities of about 10 km s −1 show no lasting impact from transient or oscillatory phenomena with maximal velocity amplitudes of only about 1 km s −1 that run along them. We could not detect any clear correlation of the location and evolution of IEF channels to local magnetic field properties in the photosphere in the penumbra or moving magnetic features in the sunspot moat. Our results support a picture of the IEF as a field-aligned siphon flow along arched loops. From our data we cannot determine if their evolution is controlled by events at the outer end in the moat or at the inner end in the penumbra.

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“…The utility of Stokes inversion algorithms has resulted in the outputs being employed in various studies ( [24][25][26][27][28][29][30][31][32]; to name some recent examples) and are a key technique in establishing and analysing height varying physical parameters in solar observations. In terms of wave phenomena the view is much less clear.…”

Section: Introductionmentioning

confidence: 99%

On the effect of oscillatory phenomena on Stokes inversion results

Keys

Steiner

Vigeesh

2020

Phil. Trans. R. Soc. A.

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Stokes inversion codes are crucial in returning properties of the solar atmosphere, such as temperature and magnetic field strength. However, the success of such algorithms to return reliable values can be hindered by the presence of oscillatory phenomena within magnetic wave guides. Returning accurate parameters is crucial to both magnetohydrodynamics (MHD) studies and solar physics in general. Here, we employ a simulation featuring propagating MHD waves within a flux tube with a known driver and atmospheric parameters. We invert the Stokes profiles for the 6301 Å and 6302 Å line pair emergent from the simulations using the well-known Stokes Inversions from Response functions code to see if the atmospheric parameters can be returned for typical spatial resolutions at ground-based observatories. The inversions return synthetic spectra comparable to the original input spectra, even with asymmetries introduced in the spectra from wave propagation in the atmosphere. The output models from the inversions match closely to the simulations in temperature, line-of-sight magnetic field and line-of-sight velocity within typical formation heights of the inverted lines. Deviations from the simulations are seen away from these height regions. The inversions results are less accurate during passage of the waves within the line formation region. The original wave period could be recovered from the atmosphere output by the inversions, with empirical mode decomposition performing better than the wavelet approach in this task. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

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Magnetic Properties and Flow Angle of the Inverse Evershed Flow at Its Downflow Points

Cited by 17 publications

References 63 publications

How rare are counter Evershed flows?

How rare are counter Evershed flows?

Temporal Evolution of the Inverse Evershed Flow

On the effect of oscillatory phenomena on Stokes inversion results

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