The magnetic topology of the inverse Evershed flow

Prasad, A.; Ranganathan, Mohanakrishna; Beck, C.; Choudhary, Debi Prasad; Hu, Qiang

doi:10.1051/0004-6361/202142585

Cited by 3 publications

(3 citation statements)

References 74 publications

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“…Furthermore, we do not unambiguously detect blueshifts at the other end of the loops, which would provide evidence for a siphon flow (Cargill & Priest 1980;Straus et al 2015;Prasad et al 2022). The LB along with the network flux region are redshifted, which raises questions on how any flow would be sustained for a period of days.…”

Section: Lb Energy Budgetmentioning

confidence: 59%

Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge

Louis

Mathew

Bayanna

et al. 2023

ApJ

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Sunspot light bridges (LBs) exhibit a wide range of short-lived phenomena in the chromosphere and transition region. In contrast, we use here data from the Multi-Application Solar Telescope (MAST), the Interface Region Imaging Spectrograph (IRIS), Hinode, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) to analyze the sustained heating over days in an LB in a regular sunspot. Chromospheric temperatures were retrieved from the MAST Ca ii and IRIS Mg ii lines by nonlocal thermodynamic equilibrium inversions. Line widths, Doppler shifts, and intensities were derived from the IRIS lines using Gaussian fits. Coronal temperatures were estimated through the differential emission measure, while the coronal magnetic field was obtained from an extrapolation of the HMI vector field. At the photosphere, the LB exhibits a granular morphology with field strengths of about 400 G and no significant electric currents. The sunspot does not fragment, and the LB remains stable for several days. The chromospheric temperature, IRIS line intensities and widths, and AIA 171 and 211 Å intensities are all enhanced in the LB with temperatures from 8000 K to 2.5 MK. Photospheric plasma motions remain small, while the chromosphere and transition region indicate predominantly redshifts of 5–20 km s−1 with occasional supersonic downflows exceeding 100 km s−1. The excess thermal energy over the LB is about 3.2 × 1026 erg and matches the radiative losses. It could be supplied by magnetic flux loss of the sunspot (7.5 × 1027 erg), kinetic energy from the increase in the LB width (4 × 1028 erg), or freefall of mass along the coronal loops (6.3 × 1026 erg).

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Section: Lb Energy Budgetmentioning

confidence: 59%

Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge

Louis

Mathew

Bayanna

et al. 2023

ApJ

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“…The flow could be directed from the foot point of a flux tube with weaker magnetic field strength. Following the procedures in Prasad et al (2022), we tested this hypothesis by comparing the field strength of the field line foot points in a nonlinear force-free field extrapolation model (Wiegelmann et al 2012). Unfortunately, the result is inconclusive.…”

Section: On the Origin Of A Large Photospheric Doppler Shiftmentioning

confidence: 99%

Large Photospheric Doppler Shift in Solar Active Region 12673. I. Field-aligned Flows

Liu 刘,

Sun 孙,

Schuck

et al. 2023

ApJ

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Delta (δ) sunspots sometimes host fast photospheric flows along the central magnetic polarity inversion line (PIL). Here we study the strong Doppler shift signature in the central penumbral light bridge of solar active region NOAA 12673. Observations from the Helioseismic and Magnetic Imager (HMI) indicate highly sheared and strong magnetic fields. Large Doppler shifts up to 3.2 km s−1 appeared during the formation of the light bridge and persisted for about 16 hr. A new velocity estimator, called DAVE4VMwDV, reveals fast converging and shearing motion along the PIL from HMI vector magnetograms, and recovers the observed Doppler signal much better than an old version of the algorithm. The inferred velocity vectors are largely (anti-)parallel to the inclined magnetic fields, suggesting that the observed Doppler shift contains a significant contribution from the projected field-aligned flows. High-resolution observations from the Hinode/Spectro-Polarimeter further exhibit a clear correlation between the Doppler velocity and the cosine of the magnetic inclination, which is in agreement with HMI results and consistent with a field-aligned flow of about 9.6 km s−1. The complex Stokes profiles suggest significant gradients of physical variables along the line of sight. We discuss the implications on the δ-spot magnetic structure and the flow-driving mechanism.

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“…Chromospheric fine-scale fibrilar structures are intricately connected to the local magnetic field distribution and are thought to act as tracers for the local magnetic field topology, much like apparent coronal loops are used as proxies for the magnetic field in the lower corona (Prasad et al 2022). In the quiet Sun (QS) network, chromospheric fine structures create rosettes (bushes), which are clusters of elongated mottles expanding radially around a common center over internetwork regions.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Solar Plage Chromosphere with DKIST

Kuridze,

Uitenbroek,

Wöger

et al. 2024

ApJ

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The strongly coupled hydrodynamic, magnetic, and radiation properties of the plasma in the solar chromosphere make it a region of the Sun's atmosphere that is poorly understood. We use data obtained with the high-resolution Visible Broadband Imager (VBI) equipped with an Hβ filter and the Visible Spectro-Polarimeter (ViSP) on the Daniel K. Inouye Solar Telescope to investigate the fine-scale structure of the plage chromosphere. To aid in the interpretation of the VBI imaging data, we also analyze spectra from the CHROMospheric Imaging Spectrometer on the Swedish Solar Telescope. The analysis of spectral properties, such as enhanced line widths and line depths, explains the high contrast of the fibrils relative to the background atmosphere demonstrating that Hβ is an excellent diagnostic for the enigmatic fine-scale structure of the chromosphere. A correlation between the parameters of the Hβ line indicates that opacity broadening created by overdense fibrils could be the main reason for the spectral line broadening frequently observed in chromospheric fine-scale structures. Spectropolarimetric inversions of the ViSP data in the Ca ii 8542 Å and Fe i 6301/6302 Å lines are used to construct semiempirical models of the plage atmosphere. Inversion outputs indicate the existence of dense fibrils in the Ca ii 8542 Å line. The analyses of the ViSP data show that the morphological characteristics, such as orientation, inclination, and length of fibrils, are defined by the topology of the magnetic field in the photosphere. Chromospheric maps reveal a prominent magnetic canopy in the area where fibrils are directed toward the observer.

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The magnetic topology of the inverse Evershed flow

Cited by 3 publications

References 74 publications

Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge

Sustained Heating of the Chromosphere and Transition Region Over a Sunspot Light Bridge

Large Photospheric Doppler Shift in Solar Active Region 12673. I. Field-aligned Flows

Insight into the Solar Plage Chromosphere with DKIST

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