Comparison of inversion codes for polarized line formation in MHD simulations

Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, Reza; Rempel, Matthias

doi:10.1051/0004-6361/201424584

Cited by 46 publications

(37 citation statements)

References 57 publications

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“…This is a consequences of two effects. Firstly, these inversions assume that these parameters are constant with height, which as a result gives a value that is an average of the height profile of an atmospheric parameter weighted appropriate response function of the spectral line (Borrero et al 2014). Secondly, both magnetic field strength and velocity change rapidly with height, especially in this run which starts with a specific magnetic field setup.…”

Section: A Simulated Eventmentioning

confidence: 99%

Photospheric Response to an Ellerman Bomb-like Event—An Analogy of Sunrise/IMaX Observations and MHD Simulations

Danilović¹,

Solanki²,

Barthol³

et al. 2017

ApJS

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Ellerman Bombs are signatures of magnetic reconnection, which is an important physical process in the solar atmosphere. How and where they occur is a subject of debate. In this paper we analyse Sunrise/IMaX data together with 3D MHD simulations that aim to reproduce the exact scenario proposed for the formation of these features. Although the observed event seems to be more dynamic and violent than the simulated one, simulations clearly confirm the basic scenario for the production of EBs. The simulations also reveal the full complexity of the underlying process. The simulated observations show that the Fe I 525.02 nm line gives no information on the height where reconnection takes place. It can only give clues about the heating in the aftermath of the reconnection. The information on the magnetic field vector and velocity at this spatial resolution is, however, extremely valuable because it shows what numerical models miss and how they can be improved.-2 -

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Section: A Simulated Eventmentioning

confidence: 99%

Photospheric Response to an Ellerman Bomb-like Event—An Analogy of Sunrise/IMaX Observations and MHD Simulations

Danilović¹,

Solanki²,

Barthol³

et al. 2017

ApJS

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“…We have calculated the response functions of the spectral lines at 1565 nm (Table 1) and at 630 nm using the average penumbral model previously mentioned. The contribution from each of the four Stokes parameters has been taken into account following the method described in Borrero et al (2014). Figure 10 presents the wavelength-integrated response functions to the magnetic field strength B (topleft), magnetic field inclination with respect to the observer's line-of-sight γ (top-right), temperature T (bottomleft), and line-of-sight velocity v los (bottom-right).…”

Section: How Deep Are We Probing?mentioning

confidence: 99%

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Borrero

Ramos

Collados

et al. 2016

A&A

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Context. Some models for the topology of the magnetic field in sunspot penumbrae predict the existence of field-free or dynamically weak-field regions in the deep Photosphere. Aims. To confirm or rule out the existence of weak-field regions in the deepest photospheric layers of the penumbra. Methods. The magnetic field at log τ5 = 0 is investigated by means of inversions of spectropolarimetric data of two different sunspots located very close to disk center with a spatial resolution of approximately 0.4-0.45 ′′ . The data have been recorded using the GRIS instrument attached to the 1.5-meters GREGOR solar telescope at El Teide observatory. It includes three Fe i lines around 1565 nm, whose sensitivity to the magnetic field peaks at half a pressure-scale-height deeper than the sensitivity of the widely used Fe i spectral line pair at 630 nm. Prior to the inversion, the data is corrected for the effects of scattered light using a deconvolution method with several point spread functions. Results. At log τ5 = 0 we find no evidence for the existence of regions with dynamically weak (B < 500 Gauss) magnetic fields in sunspot penumbrae. This result is much more reliable than previous investigations done with Fe i lines at 630 nm. Moreover, the result is independent of the number of nodes employed in the inversion, and also independent of the point spread function used to deconvolve the data, and does not depend on the amount of straylight (i.e. wide-angle scattered light) considered.

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“…We also simultaneously inverted the Si i line which returned the same results as the SIR code (see Borrero et al 2014 for a detailed comparison of the two codes).…”

Section: Inversion Of Spectropolarimetric Datamentioning

confidence: 99%

Multiwavelength spectropolarimetric observations of an Ellerman bomb

Rezaei

Beck

2015

A&A

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Context. Ellerman bombs (EBs) are enhanced emission in the wings of the Hα line in the solar spectrum. Aims. We study the structure of an EB in the photosphere and chromosphere.Methods. We analyze simultaneous observations of four chromospheric lines (Hα, Ca ii H, Ca ii IR 854 nm, and He i 1083 nm) as well as two photospheric lines (Fe i 630 and Si i 1082.7 nm) along with high-cadence 160 and 170 nm ultraviolet (UV) continuum filtergrams. Full Stokes data from the Helioseismic and Magnetic Imager (HMI) are used to trace the temporal evolution of the magnetic structure.Results. We identify the EB by excess emission in the wings of the Hα line, a brightening in the UV continuum, and large emission peaks in the core of the two Ca ii lines. The EB shows a blueshift in all chromospheric lines, while no shifts are observed in the photospheric lines. The blueshift in the chromospheric layer causes very asymmetric emission peaks in the Ca ii H line. The photospheric Si i spectral line shows a shallower line depth at the location of the EB. The UV continuum maps show that the EB was substantially brighter than its surroundings for about 30 min. The continuum contrast of the EB from 170 nm to 1080 nm shows a power-law dependency on the wavelength. The temperature enhancement amounts to 130 K in the low photosphere and 400 K at the temperature minimum level. This temperature excess is also seen in an LTE inversion of the Ca ii spectra. The total thermal and radiative energy content of the EB is about 10 20 J and 10 18 J in the photosphere and chromosphere, respectively. The HMI data hints at a photospheric magnetic flux cancellation as the driver of the EB. Conclusions. Ellerman bombs release the energy in a height range of several pressure scale heights around the temperature minimum such that they affect both the photosphere and the lower chromosphere.

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Comparison of inversion codes for polarized line formation in MHD simulations

Cited by 46 publications

References 57 publications

Photospheric Response to an Ellerman Bomb-like Event—An Analogy of Sunrise/IMaX Observations and MHD Simulations

Photospheric Response to an Ellerman Bomb-like Event—An Analogy of Sunrise/IMaX Observations and MHD Simulations

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Multiwavelength spectropolarimetric observations of an Ellerman bomb

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