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Zhang, H.; Labonte, B. J.; Li, J.; Sakurai, Takashi

doi:10.1023/a:1023246421309

Cited by 30 publications

(9 citation statements)

References 15 publications

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“…The latter comparison attempted to evaluate the performance of two vector-field data sources, which means including the additional complications of the linear polarization and its data products (the component of the field perpendicular, or transverse to, the line of sight, and its azimuthal angle) in addition to the circular polarization and line-of-sight magnetic field component. Such an effort is not new Varsik, 1995;Bao et al, 2000;Zhang et al, 2003), and the effort required has not become simpler with time.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Leka

Barnes

2011

Sol Phys

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Different methods for simulating the effects of spatial resolution on magnetic field maps are compared, including those commonly used for inter-instrument comparisons. The investigation first uses synthetic data, and the results are confirmed with Hinode/SpectroPolarimeter data. Four methods are examined, one which manipulates the Stokes spectra to simulate spatial-resolution degradation, and three "post-facto" methods where the magnetic field maps are manipulated directly. Throughout, statistical comparisons of the degraded maps with the originals serve to quantify the outcomes. Overall, we find that areas with inferred magnetic fill fractions close to unity may be insensitive to optical spatial resolution; areas of sub-unity fill fractions are very sensitive. Trends with worsening spatial resolution can include increased average field strength, lower total flux, and a field vector oriented closer to the line of sight. Further-derived quantities such as vertical current density show variations even in areas of high average magnetic fill fraction. In short, unresolved maps fail to represent the distribution of the underlying unresolved fields, and the "postfacto" methods generally do not reproduce the effects of a smaller telescope aperture. It is argued that selecting a method in order to reconcile disparate spatial resolution effects should depend on the goal, as one method may better preserve the field distribution, while another can reproduce spatial resolution degradation. The results presented should help direct future inter-instrument comparisons.

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Section: Introductionmentioning

confidence: 99%

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Leka

Barnes

2011

Sol Phys

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show abstract

Section: Introductionmentioning

confidence: 99%

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Leka¹,

Barnes²

2011

Solar Flare Magnetic Fields and Plasmas

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Different methods for simulating the effects of spatial resolution on magnetic field maps are compared, including those commonly used for inter-instrument comparisons. The investigation first uses synthetic data, and the results are confirmed with Hinode/SpectroPolarimeter data. Four methods are examined, one which manipulates the Stokes spectra to simulate spatial-resolution degradation, and three "post-facto" methods where the magnetic field maps are manipulated directly. Throughout, statistical comparisons of the degraded maps with the originals serve to quantify the outcomes. Overall, we find that areas with inferred magnetic fill fractions close to unity may be insensitive to optical spatial resolution; areas of sub-unity fill fractions are very sensitive. Trends with worsening spatial resolution can include increased average field strength, lower total flux, and a field vector oriented closer to the line of sight. Further-derived quantities such as vertical current density show variations even in areas of high average magnetic fill-fraction. In short, unresolved maps fail to represent the distribution of the underlying unresolved fields, and the "post-facto" methods generally do not reproduce the effects of a smaller telescope aperture. It is argued that selecting a method in order to reconcile disparate spatial resolution effects should depend on the goal, as one method may better preserve the field distribution, while another can reproduce spatial resolution degradation. The results presented should help direct future inter-instrument comparisons.

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“…The general conclusion is that the longitudinal fields agree better than transversal fields among magnetograms from three observatories, and the agreement of vector fields is better between BBSO and HSOS than between BBSO and MSO. Zhang et al (2003) analyzed the vector magnetograms from HSOS, MSO and National Astronomical Observatory of Japan, and found that there is a basic agreement on the transversal fields among these magnetographs. In this paper, we have a comparison of magnetic field strength, inclination and azimuth between SMFT and HMI, and conclude that these two instruments have good consistency.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Improved magnetogram calibration of Solar Magnetic Field Telescope and its comparison with the Helioseismic and Magnetic Imager

Bai

Deng

Teng

et al. 2014

Monthly Notices of the Royal Astronomical Society

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In this paper, we try to improve the magnetogram calibration method of the Solar Magnetic Field Telescope (SMFT). The improved calibration process fits the observed full Stokes information, using six points on the profile of Fe ı 5324.18Å line, and the analytical Stokes profiles under the Milne-Eddington atmosphere model, adopting the Levenberg-Marquardt least-square fitting algorithm. In Comparison with the linear calibration methods, which employs one point, there is large difference in the strength of longitudinal field B l and tranverse field B t , caused by the non-linear relationship, but the discrepancy is little in the case of inclination and azimuth. We conclude that it is better to deal with the non-linear effects in the calibration of B l and B t using six points. Moreover, in comparison with SDO/HMI, SMFT has larger stray light and acquires less magnetic field strength. For vector magnetic fields in two sunspot regions, the magnetic field strength, inclination and azimuth angles between SMFT and HMI are roughly in agrement, with the linear fitted slope of 0.73/0.7, 0.95/1.04 and 0.99/1.1. In the case of pores and quiet regions (B l < 600 G), the fitted slopes of the longitudinal magnetic field strength are 0.78 and 0.87 respectively.

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Untitled

Cited by 30 publications

References 15 publications

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps

Improved magnetogram calibration of Solar Magnetic Field Telescope and its comparison with the Helioseismic and Magnetic Imager

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