The Hinode Spectro-Polarimeter

Lites, B. W.; Akin, David L.; Card, G.; Cruz, T.; Duncan, D.; Edwards, Christopher G.; Elmore, D.; Hoffmann, C.; Katsukawa, Y.; Katz, N.; Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Shine, R. A.; Streander, K. V.; Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S.

doi:10.1007/s11207-012-0206-3

Cited by 183 publications

(133 citation statements)

References 15 publications

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“…This implies that for an accurate derivation of temperatures from observed spectra the stray-light offset has to be corrected before an inversion. On the positive side, the stray-light offset β inside the SP spectrograph was found to be below 3% (see also Lites et al 2013), which makes these data and data of similar spectral quality well suited for a derivation of temperature stratifications in the solar photosphere (e.g. Socas-Navarro 2011).…”

Section: Summary and Discussionmentioning

confidence: 80%

Thermodynamic fluctuations in solar photospheric three-dimensional convection simulations and observations

Beck

Fabbian

Moreno‐Insertis

et al. 2013

A&A

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Context. Numerical three-dimensional (3D) radiative (magneto-)hydrodynamical [(M)HD] simulations of solar convection are nowadays used to understand the physical properties of the solar photosphere and convective envelope, and, in particular, to determine the Sun's photospheric chemical abundances. To validate this approach, it is important to check that no excessive thermodynamic fluctuations arise as a consequence of the partially incomplete treatment of radiative transfer causing radiative damping that is too modest. Aims. We investigate the realism of the thermodynamics in recent state-of-the-art 3D convection simulations of the solar atmosphere carried out with the Stagger code.Methods. We compared the characteristic properties of several Fe i lines (557.6 nm, 630 nm, 1565 nm) and one Si i line at 1082.7 nm in solar disc-centre observations of different spatial resolution with spectra synthesized from 3D convection simulations. The observations were taken with ground-based (Echelle spectrograph, Göttingen Fabry-Pérot Interferometer (GFPI), POlarimetric LIttrow Spectrograph, Tenerife Infrared Polarimeter, all at the Vacuum Tower Telescope on Tenerife) and space-based instruments (Hinode/Spectropolarimeter). We degraded the synthetic spectra to the spatial resolution of the observations, based on the distribution of the continuum intensity I c . We estimated the spectral degradation to be applied to the simulation results by comparing atlas spectra with averaged observed spectra. In addition to deriving a set of line parameters directly from the intensity profiles, we used the SIR (Stokes Inversion based on Response functions) code to invert the spectra. Results. The spatial degradation kernels yield a similar generic spatial stray-light contamination of about 30% for all instruments. The spectral stray light inside the different spectrometers is found to be between 2% and 20%. Most of the line parameters from the observational data are matched by the degraded HD simulation spectra. The inversions predict a macroturbulent velocity v mac below 10 m s −1 for the HD simulation spectra at full spatial resolution, whereas they yield v mac 1000 m s −1 at a spatial resolution of 0. 3. The temperature fluctuations in the inversion of the degraded HD simulation spectra do not exceed those from the observational data (of the order of 100−200 K rms for −2 log τ 500 nm −0.5). The comparison of line parameters in spatially averaged profiles with the averaged values of line parameters in spatially resolved profiles indicates a significant change in (average) line properties on a spatial scale between 0. 13 and 0. 3. Conclusions. Up to a spatial resolution of 0. 3 (GFPI spectra), we find no indications of excessive thermodynamic fluctuations in the 3D HD simulation. To definitely confirm that simulations without spatial degradation contain fully realistic thermodynamic fluctuations requires observations at even higher spatial resolution (i.e. <0. 13).

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Section: Summary and Discussionmentioning

confidence: 80%

Thermodynamic fluctuations in solar photospheric three-dimensional convection simulations and observations

Beck

Fabbian

Moreno‐Insertis

et al. 2013

A&A

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“…There are additional instrumental artifacts that may or may not be mitigated fully. In this section, some rudimentary evaluation of the evolution of AR #11158 features are discussed in light of the limitations of the data, and a brief qualitative comparison is presented with simultaneous observations from the Hinode/SpectroPolarimeter (Kosugi et al, 2007;Tsuneta et al, 2008;Lites et al, 2013). Comparisons beyond the qualitative presentations made here are beyond the scope of this paper.…”

Section: Limits and Validationmentioning

confidence: 99%

The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance

et al. 2014

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The Helioseismic and Magnetic Imager (HMI) began near-continuous full-disk solar measurements on 1 May 2010 from the Solar Dynamics Observatory (SDO). An automated processing pipeline keeps pace with observations to produce observable quantities, including the photospheric vector magnetic field, from sequences of filtergrams. The basic vector-field frame list cadence is 135 seconds, but to reduce noise the filtergrams are combined to derive data products every 720 seconds. The primary 720 s observables were released in mid-2010, including Stokes polarization parameters measured at six wavelengths, as well as intensity, Doppler velocity, and the line-of-sight magnetic field. More advanced products, including the full vector magnetic field, are now available. Automatically identified HMI Active Region Patches (HARPs) track the location and shape of magnetic regions throughout their lifetime.The vector field is computed using the Very Fast Inversion of the Stokes Vector (VFISV) code optimized for the HMI pipeline; the remaining 180 • azimuth ambiguity is resolved with the Minimum Energy (ME0) code. The Milne-Eddington inversion is performed on all full-disk HMI observations. The disambiguation, until recently run only on HARP regions, is now implemented for the full disk. Vector and scalar quantities in the patches are used to derive active region indices potentially useful for forecasting; the data maps and indices are collected in the SHARP data series, hmi.sharp_720s. Definitive SHARP processing is completed only after the region rotates off the visible disk; quick-look products are produced in near real time. Patches are provided in both CCD and heliographic coordinates.HMI provides continuous coverage of the vector field, but has modest spatial, spectral, and temporal resolution. Coupled with limitations of the analysis and interpretation techniques, effects of the orbital velocity, and instrument performance, the resulting measurements have a certain dynamic range and sensitivity and are subject to systematic errors and uncertainties that are characterized in this report.

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“…The SOT/SP instrument (Lites et al 2013) of the Solar Optical Telescope (Tsuneta et al 2008) is on board the Hinode mission (Kosugi et al 2007). Stokes profiles and level 2 outputs from inversions using the HAO "MERLIN" inversion code developed under the Community Spectro-polarimetric Analysis Center are available online 2 .…”

Section: Broadening Function For Instrumental Effects In Sot/sp Datamentioning

confidence: 99%

Fast inversion of Zeeman line profiles using central moments

Mein

Uitenbroek

Mein

et al. 2016

A&A

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Context. In the case of unresolved solar structures or stray light contamination, inversion techniques using four Stokes parameters of Zeeman profiles cannot disentangle the combined contributions of magnetic and nonmagnetic areas to the observed Stokes I. Aims. In the framework of a two-component model atmosphere with filling factor f , we propose an inversion method restricting input data to Q , U, and V profiles, thus overcoming ambiguities from stray light and spatial mixing. Methods. The V-moments inversion (VMI) method uses shifts S V derived from moments of V-profiles and integrals of Q 2 , U 2 , and V 2 to determine the strength B and inclination ψ of a magnetic field vector through least-squares polynomial fits and with very few iterations. Moment calculations are optimized to reduce data noise effects. To specify the model atmosphere of the magnetic component, an additional parameter δ, deduced from the shape of V-profiles, is used to interpolate between expansions corresponding to two basic models. Results. We perform inversions of HINODE SOT/SP data for inclination ranges 0 < ψ < 60 • and 120 < ψ < 180 • for the 630.2 nm Fe i line. A damping coefficient is fitted to take instrumental line broadening into account. We estimate errors from data noise.Magnetic field strengths and inclinations deduced from VMI inversion are compared with results from the inversion codes UNNOFIT and MERLIN. Conclusions. The VMI inversion method is insensitive to the dependence of Stokes I profiles on the thermodynamic structure in nonmagnetic areas. In the range of B f products larger than 200 G, mean field strengths exceed 1000 G and there is not a very significant departure from the UNNOFIT results because of differences between magnetic and nonmagnetic model atmospheres. Further improvements might include additional parameters deduced from the shape of Stokes V profiles and from large sets of 3D-MHD simulations, especially for unresolved magnetic flux tubes.

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The Hinode Spectro-Polarimeter

Cited by 183 publications

References 15 publications

Thermodynamic fluctuations in solar photospheric three-dimensional convection simulations and observations

Thermodynamic fluctuations in solar photospheric three-dimensional convection simulations and observations

The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance

Fast inversion of Zeeman line profiles using central moments

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