Downflows in sunspot umbral dots

We study the velocity field of umbral dots at a resolution of 0.14". Our analysis is based on full Stokes spectropolarimetric measurements of a pore taken with the CRISP instrument at the Swedish 1-m Solar Telescope. We determine the flow velocity at different heights in the photosphere from a bisector analysis of the Fe I 630 nm lines. In addtion, we use the observed Stokes Q, U, and V profiles to characterize the magnetic properties of these structures. We find that most umbral dots are associated with strong upflows in deep photospheric layers. Some of them also show concentrated patches of downflows at their edges, with sizes of about 0.25", velocities of up to 1000 m/s, and enhanced net circular polarization signals. The downflows evolve rapidly and have lifetimes of only a few minutes. These results appear to validate numerical models of magnetoconvection in the presence of strong magnetic fields.Comment: Final published version. For best quality figures, please download the PS versio

CRISP Spectropolarimetric Imaging of Penumbral Fine Structure

We discuss penumbral fine structure in a small part of a pore, observed with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST), close to its diffraction limit of 0.16 arcsec. Milne-Eddington inversions applied to these Stokes data reveal large variations of field strength and inclination angle over dark-cored penumbral intrusions and a dark-cored light bridge. The mid-outer part of this penumbra structure shows 0.3 arcsec wide spines, separated by 1.6 arcsec (1200 km) and associated with 30 deg inclination variations. Between these spines, there are no small-scale magnetic structures that easily can be be identified with individual flux tubes. A structure with nearly 10 deg more vertical and weaker magnetic field is seen midways between two spines. This structure is co-spatial with the brightest penumbral filament, possibly indicating the location of a convective upflow from below.Comment: Accepted for publication in ApJL 17 Oct 2008. One Figure adde

Geographic variations in possible risk factors for severe cardiac malformations

The aim of this study was to investigate various putative risk factors in a county in Sweden, described as having a 28% increased prevalence of cardiovascular malformations, and to compare them with the risk factors in two reference counties. Women giving birth in the studied counties differed in age and parity distribution, smoking, and educational level but these differences could not explain the increased risk of cardiovascular malformations in the county, since after stratification for these variables, the risk, estimate did not change substantially. A number of potential risk factors were studied in a case/control design: spontaneous abortions, involuntary childlessness, maternal disease, body mass index, medical drug use, alcohol use, parental employment, paternal age, and urban/rural residency. No single factor could be attributed to the increased rate, with the exception of living in a rural district, Nearly all risk factors, however, were stronger in the county studied than those in the reference counties (0.02 > p > 0.01). Conclusion: The only single putative risk factor that could have contributed to the increased risk for cardiac defects described in the county Studied was maternal residency in a rural district. Notably, nearly all potential risk factors studied were stronger in the counts studied compared with those in the reference area. A conceivable explanation is that one or more unidentified factors related to rural residency could potentiate prevalent and weak teratogenic risk factors for cardiac defects