Enhanced Acoustic Emission in Relation to the Acoustic Halo Surrounding Active Region 11429

The use of acoustic holography in the high-frequency $p$-mode spectrum can resolve the source distributions of enhanced acoustic emissions within halo structures surrounding active regions. In doing so, statistical methods can then be applied to ascertain relationships with the magnetic field. This is the focus of this study. The mechanism responsible for the detected enhancement of acoustic sources around solar active regions has not yet been explained. Furthermore the relationship between the magnetic field and enhanced acoustic emission has not yet been comprehensively examined. We have used vector magnetograms from the \Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory (SDO) to image the magnetic-field properties in the halo. We have studied the acoustic morphology of an active region, with a complex halo and "glories," and we have linked some acoustic properties to the magnetic-field configuration. In particular, we find that acoustic sources are significantly enhanced in regions of intermediate field strength with inclinations no different from the distributions found in the quiet Sun. Additionally we have identified a transition region between the active region and the halo, in which the acoustic source power is hindered by inclined fields of intermediate field strength. Finally, we have compared the results of acoustic emission maps, calculated from holography, and the commonly used local acoustic maps, finding that the two types of maps have similar properties with respect to the magnetic field but lack spatial correlation when examining the highest-powered regions.Comment: 19 pages, 8 figures, Accepted by Solar Physic

Modelling and Interpreting The Effects of Spatial Resolution on Solar Magnetic Field Maps

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 {\it 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.Comment: Accepted for publication in Solar Physics. The final publication (including full-resolution figures) will be available at http://www.springerlink.co

The changing landscape of OSH regulation in the UK

This report presents key findings of a research project on the changing landscape of OSH regulation in the UK. Understanding the changing landscape of OSH regulation and standards and its implications are of central importance for ensuring that OSH outcomes are not compromised and the needs of different types of organisations are met. This project examined the landscape of OSH in the UK since its origin and in particular looked at how regulation of OSH has evolved over time. It considered both policy and practice issues as well as the role of key stakeholders in this process with a view to identify how the right balance can be achieved to promote health and safety going forward. To achieve its aims, a qualitative methodology was implemented in five stages: a. a literature and policy review, including a comparative analysis with other countries; b. case study analysis; c. stakeholder interviews, d. stakeholder workshops including focus groups; and e. research output synthesis

Resolving the Azimuthal Ambiguity in Vector Magnetogram Data with the Divergence-Free Condition: Application to Discrete Data

We investigate how the divergence-free property of magnetic fields can be exploited to resolve the azimuthal ambiguity present in solar vector magnetogram data, by using line-of-sight and horizontal heliographic derivative information as approximated from discrete measurements. Using synthetic data we test several methods that each make different assumptions about how the divergence-free property can be used to resolve the ambiguity. We find that the most robust algorithm involves the minimisation of the absolute value of the divergence summed over the entire field of view. Away from disk centre this method requires the sign and magnitude of the line-of-sight derivatives of all three components of the magnetic field vector.Comment: Solar Physics, in press, 20 pages, 11 figure

Sinteza i karakterizacija kompleksa cink(II), kadmijum(II), platina(II),i paladijum(II) sa kalijum-3-ditiokarboksi-3-aza-5-aminopentanoatom

Complexes of zinc(lI), cadmium(II). platinum(lI) and palladium(II) with a new poly-dentate dithiocarbamate ligand, 3-dithiocarboxy-3-aza-5-aminopentanoate (daap(-)), of the type M(daap)(2).nH(2)O (M = Zn(II), Cd(II), n = 2, or M = Pt(II) Pd(II) n = 0). have been prepared and characterized by elemental analysis. IR and UV/VIS spectroscopy, as well as magnetic measurements. The spectra of the complexes suggest a bidentate coordination of the daap- ligand to the metal ions via the sulfur atoms of the deprotonated dithiocarbamato group. The fact that under the same experimental conditions its S-methyl ester does not form complexes could be taken as proof of the suggested coordination mode.Reakcijom između cink(II), kadmijum(II), platina(II) i paladijum(II)-soli i kalijum- 3-ditiokarboksi-3-aza-5-aminopentanoata dobijeni su dogovarajući kompleksi tipa M(daap)2.nH2O. Izolovani kompleksi su okarakterisani elementarnom analizom, IR i UV/VIS spektroskopijom kao i merenjem magnetnih susceptibiliteta. Spektri kompleksa sugerišu bidentatnu koordinaciju daap liganda sa navedenim metalnim jonima preko atoma sumpora deprotonovane ditiokarbamato grupe. Kao dokaz navedenog načina koordinacije može poslužiti činjenica da pri istim eksperimentalnim uslovima S-metil estar liganda ne daje komplekse

Response to "Comment on `Resolving the 180deg Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise, Spatial Resolution, and Method Assumptions'"

We address points recently discussed in Georgoulis (2011) in reference to Leka et al. (2009b). Most importantly, we find that the results of Georgoulis (2011) support a conclusion of Leka et al. (2009b): that limited spatial resolution and the presence of unresolved magnetic structures can challenge ambiguity- resolution algorithms. Moreover, the findings of both Metcalf et al. (2006) and Leka et al. (2009b) are confirmed in Georgoulis (2011): a method's performance can be diminished when the observed field fails to conform to that method's assumptions. The implication of boundaries in models of solar magnetic structures is discussed; we confirm that the distribution of the field components in the model used in Leka et al. (2009b) is closer to what is observed on the Sun than what is proposed in Georgoulis (2011). It is also shown that method does matter with regards to simulating limited spatial resolution and avoiding an inadvertent introduction of bias. Finally, the assignment of categories to data- analysis algorithms is revisited; we argue that assignments are only useful and elucidating when used appropriately.Comment: Accepted for publication in Solar Physic

The Influence of Spatial Resolution on Nonlinear Force-Free Modeling

The nonlinear force-free field (NLFFF) model is often used to describe the solar coronal magnetic field, however a series of earlier studies revealed difficulties in the numerical solution of the model in application to photospheric boundary data. We investigate the sensitivity of the modeling to the spatial resolution of the boundary data, by applying multiple codes that numerically solve the NLFFF model to a sequence of vector magnetogram data at different resolutions, prepared from a single Hinode/SOT-SP scan of NOAA Active Region 10978 on 2007 December 13. We analyze the resulting energies and relative magnetic helicities, employ a Helmholtz decomposition to characterize divergence errors, and quantify changes made by the codes to the vector magnetogram boundary data in order to be compatible with the force-free model. This study shows that NLFFF modeling results depend quantitatively on the spatial resolution of the input boundary data, and that using more highly resolved boundary data yields more self-consistent results. The free energies of the resulting solutions generally trend higher with increasing resolution, while relative magnetic helicity values vary significantly between resolutions for all methods. All methods require changing the horizontal components, and for some methods also the vertical components, of the vector magnetogram boundary field in excess of nominal uncertainties in the data. The solutions produced by the various methods are significantly different at each resolution level. We continue to recommend verifying agreement between the modeled field lines and corresponding coronal loop images before any NLFFF model is used in a scientific setting.Comment: Accepted to ApJ; comments/corrections to this article are welcome via e-mail, even after publicatio

Comment on "Resolving the 180-deg Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise, Spatial Resolution, and Method Assumptions"

In a recent paper, Leka at al. (Solar Phys. 260, 83, 2009)constructed a synthetic vector magnetogram representing a three-dimensional magnetic structure defined only within a fraction of an arcsec in height. They rebinned the magnetogram to simulate conditions of limited spatial resolution and then compared the results of various azimuth disambiguation methods on the resampled data. Methods relying on the physical calculation of potential and/or non-potential magnetic fields failed in nearly the same, extended parts of the field of view and Leka et al. (2009) attributed these failures to the limited spatial resolution. This study shows that the failure of these methods is not due to the limited spatial resolution but due to the narrowly defined test data. Such narrow magnetic structures are not realistic in the real Sun. Physics-based disambiguation methods, adapted for solar magnetic fields extending to infinity, are not designed to handle such data; hence, they could only fail this test. I demonstrate how an appropriate limited-resolution disambiguation test can be performed by constructing a synthetic vector magnetogram very similar to that of Leka et al. (2009) but representing a structure defined in the semi-infinite space above the solar photosphere. For this magnetogram I find that even a simple potential-field disambiguation method manages to resolve the ambiguity very successfully, regardless of limited spatial resolution. Therefore, despite the conclusions of Leka et al. (2009), a proper limited-spatial-resolution test of azimuth disambiguation methods is yet to be performed in order to identify the best ideas and algorithms.Comment: Solar Physics, in press (19 pp., 5 figures, 2 tables

Nonlinear force-free models for the solar corona I. Two active regions with very different structure

With the development of new instrumentation providing measurements of solar photospheric vector magnetic fields, we need to develop our understanding of the effects of current density on coronal magnetic field configurations. The object is to understand the diverse and complex nature of coronal magnetic fields in active regions using a nonlinear force-free model. From the observed photospheric magnetic field we derive the photospheric current density for two active regions: one is a decaying active region with strong currents (AR8151), and the other is a newly emerged active region with weak currents (AR8210). We compare the three-dimensional structure of the magnetic fields for both active region when they are assumed to be either potential or nonlinear force-free. The latter is computed using a Grad-Rubin vector-potential-like numerical scheme. A quantitative comparison is performed in terms of the geometry, the connectivity of field lines, the magnetic energy and the magnetic helicity content. For the old decaying active region the connectivity and geometry of the nonlinear force-free model include strong twist and strong shear and are very different from the potential model. The twisted flux bundles store magnetic energy and magnetic helicity high in the corona (about 50 Mm). The newly emerged active region has a complex topology and the departure from a potential field is small, but the excess magnetic energy is stored in the low corona and is enough to trigger powerful flares.Comment: 11 pages, 11 figure