9 research outputs found
Spatial variations of the SrI 4607\AA scattering polarization signals at subgranular scale observed with ZIMPOL at GREGOR telescope
Sr I 4607\AA spectral line shows one of the strongest scattering polarization
signals in the visible solar spectrum. The amplitudes of these signals are
expected to vary at granular spatial scales. This variation can be due to
changes in the magnetic field intensity and orientation (Hanle effect) as well
as due to spatial and temporal variations in the plasma properties. Measuring
the spatial variation of such polarization signal would allow us to study the
properties of the magnetic fields at subgranular region. But, the observations
are challenging since both high spatial resolution and high spectropolarimetric
sensitivity are required at the same time. To the aim of measuring these
spatial variations at granular scale, we carried out a spectro-polarimetric
measurement with the Zurich IMaging POLarimeter (ZIMPOL), at the GREGOR solar
telescope at different limb distances on solar disk. Our results show a spatial
variation of scattering linear polarization signals in Sr I 4607\AA line at the
granular scale at every , starting from 0.2 to 0.8. The correlation
between the polarization signal amplitude and the continuum intensity imply
statistically that the scattering polarization is higher at the granular
regions than in the intergranular lanes.Comment: 4 pages, 3 figures, Proceeding of Third Meeting of the Italian Solar
and Heliospheric Community, OCTOBER 28-31, 2018 - TURI
Observations on spatial variations of the Sr~{\sc i} 4607~\AA~scattering polarization signals at different limb distances with ZIMPOL
The Sr~{\sc i} 4607~\AA\ spectral line shows one of the strongest scattering
polarization signals in the visible solar spectrum. The amplitude of this
polarization signal is expected to vary at granular spatial scales, due to the
combined action of the Hanle effect and the local anisotropy of the radiation
field. Observing these variations would be of great interest because it would
provide precious information on the small-scale activity of the solar
photosphere. At present, few detections of such spatial variations have been
reported. This is due to the difficulty of these measurements, which require
combining high spatial ( 0.1"), spectral ( 20 m\AA), and temporal
resolution (< 1 min) with increased polarimetric sensitivity (
10). Aims. We aim to detect spatial variations at granular scales of
the scattering polarization peak of the Sr~{\sc i} 4607~\AA\ line at different
limb distances, and to study the correlation with the continuum intensity.
Methods.Using the Zurich IMaging POLarimeter (ZIMPOL) system mounted at the
GREGOR telescope and spectrograph in Tenerife, Spain, we carried out
spectro-polarimetric measurements to obtain the four Stokes parameters in the
Sr~{\sc i} line at different limb distances, from to , on
the solar disk. Results.Spatial variations of the scattering polarization
signal in the Sr~{\sc i} 4607~\AA\ line, with a spatial resolution of about
0.66", are clearly observed at every . The spatial scale of these
variations is comparable to the granular size. A statistical analysis reveals
that the linear scattering polarization amplitude in this Sr~{\sc i} spectral
line is positively correlated with the intensity in the continuum,
corresponding to the granules, at every .Comment: 8 pages, 6 figures, accepted for publication in A&
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
Observation and modeling of scattering polarization signals sensitive to unresolved photospheric magnetic fields via Hanle and magneto-optical effects
The main focus of this Thesis is to explore and apply techniques based on scattering polarization to study certain aspects of the solar magnetism that are not accessible through more widespread techniques. Using the ZIMPOL instrument at the GREGOR solar telescope, we measured the spatial variation of the scattering polarization signals of the Sr I 4607 Å line, whose sensitivity to Hanle effect encodes information on the small-scale magnetic fields present in the solar photosphere. Performing new observations using ZIMPOL at IRSOL and at GREGOR, we found clear observational proof that the scattering polarization wings of the chromospheric Ca I 4227 Å line are sensitive to photospheric magnetic fields via magneto-optical effects. We finally explored the diagnostic potential of such sensitivity by theoretically modeling the Ca I 4227 Å line and we identified the linear polarization angle as an observable of interest for diagnosing solar magnetic fields
The polarization angle in the wings of Ca I 4227: A new observable for diagnosing unresolved photospheric magnetic fields
Context. When observed in quiet regions close to the solar limb, many strong resonance lines show conspicuous linear polarization signals, produced by scattering processes (i.e., scattering polarization), with extended wing lobes. Recent studies indicate that, contrary to what was previously believed, the wing lobes are sensitive to the presence of relatively weak longitudinal magnetic fields through magneto-optical (MO) effects.
Aims. We theoretically investigate the sensitivity of the scattering polarization wings of the Ca