Temporal Evolution of the Inverse Evershed Flow

Beck, C.; Choudhary, Debi Prasad

doi:10.3847/1538-4357/ab75bd

Cited by 9 publications

(2 citation statements)

References 99 publications

(125 reference statements)

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“…The technique of inferring v LOS from various bisectors across a spectral line to provide height-stratified information is commonly used for photospheric lines (Kulander & Jefferies 1966;González Manrique et al 2020), such as Si I 10827 Å in the case of GM21, due to their symmetrical profiles. However there are only few examples of inferring Ca II 8542 Å bisector motions in magnetic flux tubes (e.g., Chae et al 2013;Beck & Choudhary 2020), due to a range of chromospheric effects capable of adding nonlinearities to the absorption profile. Therefore it was prudent to first ensure the spectral profiles within the pores were suitable for bisector analysis.…”

Section: Ca II 8542 å Bisectorsmentioning

confidence: 99%

The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores

Grant

Jess

Stangalini

et al. 2022

ApJ

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Solar pores are efficient magnetic conduits for propagating magnetohydrodynamic wave energy into the outer regions of the solar atmosphere. Pore observations often contain isolated and/or unconnected structures, preventing the statistical examination of wave activity as a function of the atmospheric height. Here, using high-resolution observations acquired by the Dunn Solar Telescope, we examine photospheric and chromospheric wave signatures from a unique collection of magnetic pores originating from the same decaying sunspot. Wavelet analysis of high-cadence photospheric imaging reveals the ubiquitous presence of slow sausage-mode oscillations, coherent across all photospheric pores through comparisons of intensity and area fluctuations, producing statistically significant in-phase relationships. The universal nature of these waves allowed an investigation of whether the wave activity remained coherent as they propagate. Utilizing bisector Doppler velocity analysis of the Ca ii 8542 Å line, alongside comparisons of the modeled spectral response function, we find fine-scale 5 mHz power amplification as the waves propagate into the chromosphere. Phase angles approaching zero degrees between co-spatial line depths spanning different line depths indicate standing sausage modes following reflection against the transition region boundary. Fourier analysis of chromospheric velocities between neighboring pores reveals the annihilation of the wave coherency observed in the photosphere, with examination of the intensity and velocity signals from individual pores indicating they behave as fractured waveguides, rather than monolithic structures. Importantly, this work highlights that wave morphology with atmospheric height is highly complex, with vast differences observed at chromospheric layers, despite equivalent wave modes being introduced into similar pores in the photosphere.

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Section: Ca II 8542 å Bisectorsmentioning

confidence: 99%

The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores

Grant

Jess

Stangalini

et al. 2022

ApJ

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“…This may be due to the settlment of penumbral-like connection between small flux concentrations (e.g., pores) adjacent to the main sunspot during the first phases of penumbra formation (Siu-Tapia et al 2017). Nonetheless, this photospheric counter-Evershed flow should not be confused with the inverse-Evershed flow that is usually observed in the chromosphere cospatially to the photospheric Evershed flow (Maltby 1975; see also Beck & Choudhary 2020).…”

Section: Introductionmentioning

confidence: 96%

Restoring process of sunspot penumbra

Romano,

Murabito,

Guglielmino

et al. 2020

Preprint

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We describe the disappearance of a sector of sunspot penumbra and its restoring process observed in the preceding sunspot of active region NOAA 12348. The evolution of the magnetic field and the plasma flows support the idea that the penumbra forms due to a change of inclination of the magnetic field of the canopy.Moving magnetic features have been observed during the disintegration phase of that sector of sunspot penumbra. During the restoring phase we have not observed any magnetic flux emergence around the sunspot. The restoring process of the penumbra sector completed in about 72 hours and it was accompanied by the transition from the counter-Evershed flow to the classical Evershed flow.The inversion of photospheric spectropolarimetric measurements taken by IBIS allowed us to reconstruct how the uncombed configuration of the magnetic field forms during the new settlement of the penumbra, i.e., the vertical component of the magnetic field seems to be progressively replaced by some horizontal field lines, corresponding to the intra-spines.

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The magnetic topology of the inverse Evershed flow

Prasad

Ranganathan²,

Beck

et al. 2022

A&A

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Context. The inverse Evershed flow (IEF) is a mass motion towards sunspots at chromospheric heights. Aims. We combined high-resolution observations of NOAA 12418 from the Dunn Solar Telescope and vector magnetic field measurements from the Helioseismic and Magnetic Imager (HMI) to determine the driver of the IEF. Methods. We derived chromospheric line-of-sight (LOS) velocities from spectra of Hα and Ca II IR. The HMI data were used in a non-force-free magnetic field extrapolation to track closed field lines near the sunspot in the active region. We determined their length and height, located their inner and outer foot points, and derived flow velocities along them. Results. The magnetic field lines related to the IEF reach on average a height of 3 megameter (Mm) over a length of 13 Mm. The inner (outer) foot points are located at 1.2 (1.9) sunspot radii. The average field strength difference ΔB between inner and outer foot points is +400 G. The temperature difference ΔT is anti-correlated with ΔB with an average value of −100 K. The pressure difference Δp is dominated by ΔB and is primarily positive with a driving force towards the inner foot points of 1.7 kPa on average. The velocities predicted from Δp reproduce the LOS velocities of 2–10 km s−1 with a square-root dependence. Conclusions. We find that the IEF is driven along magnetic field lines connecting network elements with the outer penumbra by a gas pressure difference that results from a difference in field strength as predicted by the classical siphon flow scenario.

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Temporal Evolution of the Inverse Evershed Flow

Cited by 9 publications

References 99 publications

The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores

The Propagation of Coherent Waves Across Multiple Solar Magnetic Pores

Restoring process of sunspot penumbra

The magnetic topology of the inverse Evershed flow

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