High Resolution Observations using Adaptive Optics: Achievements and Future Needs

Over the last few years, several interesting observations were obtained with the help of solar Adaptive Optics (AO). In this paper, few observations made using the solar AO are enlightened and briefly discussed. A list of disadvantages with the current AO system are presented. With telescopes larger than 1.5m are expected during the next decade, there is a need to develop the existing AO technologies for large aperture telescopes. Some aspects of this development are highlighted. Finally, the recent AO developments in India are also presented

Weather in stellar atmosphere: the dynamics of mercury clouds in alpha Andromedae

The formation of long-lasting structures at the surfaces of stars is commonly ascribed to the action of strong magnetic fields. This paradigm is supported by observations of evolving cool spots in the Sun and active late-type stars, and stationary chemical spots in the early-type magnetic stars. However, results of our seven-year monitoring of mercury spots in non-magnetic early-type star alpha Andromedae show that the picture of magnetically-driven structure formation is fundamentally incomplete. Using an indirect stellar surface mapping technique, we construct a series of 2-D images of starspots and discover a secular evolution of the mercury cloud cover in this star. This remarkable structure formation process, observed for the first time in any star, is plausibly attributed to a non-equilibrium, dynamical evolution of the heavy-element clouds created by atomic diffusion and may have the same underlying physics as the weather patterns on terrestrial and giant planets.Comment: 10 pages, 2 figures; to be published in Nature Physic

The Imaging Magnetograph eXperiment (IMaX) for the Sunrise balloon-borne solar observatory

The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by four institutions in Spain that flew on board the Sunrise balloon-borne telesocope in June 2009 for almost six days over the Arctic Circle. As a polarimeter IMaX uses fast polarization modulation (based on the use of two liquid crystal retarders), real-time image accumulation, and dual beam polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the instrument uses a LiNbO3 etalon in double pass and a narrow band pre-filter to achieve a spectral resolution of 85 mAA. IMaX uses the high Zeeman sensitive line of Fe I at 5250.2 AA and observes all four Stokes parameters at various points inside the spectral line. This allows vector magnetograms, Dopplergrams, and intensity frames to be produced that, after reconstruction, reach spatial resolutions in the 0.15-0.18 arcsec range over a 50x50 arcsec FOV. Time cadences vary between ten and 33 seconds, although the shortest one only includes longitudinal polarimetry. The spectral line is sampled in various ways depending on the applied observing mode, from just two points inside the line to 11 of them. All observing modes include one extra wavelength point in the nearby continuum. Gauss equivalent sensitivities are four Gauss for longitudinal fields and 80 Gauss for transverse fields per wavelength sample. The LOS velocities are estimated with statistical errors of the order of 5-40 m/s. The design, calibration and integration phases of the instrument, together with the implemented data reduction scheme are described in some detail.Comment: 17 figure

Enterprise placements: factors which support learning and prolonged attainment in students

This article investigates the learning and academic attainment of undergraduate education students on enterprise placement projects in a longitudinal mixed methods study. By observing the placement learning and analysing previous and subsequent attainment of a second and third year group it adds to the ontology of purpose for enterprise in education and concurs with the growing body of work identifying placements with sustained academic improvement. The qualitative investigation identifies five key learning factors from the placements which support improved academic attainment. These are: pressure to learn; critical personal learning events; seeing the setting as a learning environment; professional attachments, and having space to learn. These factors support the transfer of learning from one context or situation to another and using concepts of transformative learning (Mezirow 2000; Jones, Matlay, and Harris 2012) or transitional learning (Illeris 2007) contributes to a cycle of increasing self-esteem and motivation and a sustained improvement in academic attainment. It concludes that a praxis curriculum, using self-assessments, continuous short (micro) reflections and taught awareness of the placement as a place to look for and recognise learning, would underpin these five factors and contribute to the academic processes underpinning attainment

Modeling the Subsurface Structure of Sunspots

While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

Sunspots: from small-scale inhomogeneities towards a global theory

The penumbra of a sunspot is a fascinating phenomenon featuring complex velocity and magnetic fields. It challenges both our understanding of radiative magneto-convection and our means to measure and derive the actual geometry of the magnetic and velocity fields. In this contribution we attempt to summarize the present state-of-the-art from an observational and a theoretical perspective.Comment: Accepted for publication in Space Science Review

Solar Spectroscopy and (Pseudo-)Diagnostics of the Solar Chromosphere

I first review trends in current solar spectrometry and then concentrate on comparing various spectroscopic diagnostics of the solar chromosphere. Some are actually not at all chromospheric but just photospheric or clapotispheric and do not convey information on chromospheric heating, even though this is often assumed. Balmer Halpha is the principal displayer of the closed-field chromosphere, but it is unclear how chromospheric fibrils gain their large Halpha opacity. The open-field chromosphere seems to harbor most if not all coronal heating and solar wind driving, but is hardly seen in optical diagnostics.Comment: To appear in "Recent Advances in Spectroscopy: Astrophysical, Theoretical and Experimental Perspectives", eds. R.K. Chaudhuri, M.V. Mekkaden, A.V. Raveendran and A. Satya Narayanan, Astrophysics and Space Science Proceedings, Springer, Heidelberg, 2009. Revision: references corrected, new references added, minor text correction

A cognitive science analysis of the Quaker Business Method: is how it works why it works?

The Quaker Business Method (QBM) has been in development for over 300 years. Quakers believe that the QBM is an effective means for making decisions. This paper develops a tripartite theoretical framework to analyze the QBM in order to examine its efficacy, both in terms of the quality of its processes and the morality of its decisions. The framework encompasses: (1) a decomposition of the QBM as a set of tools; (2) a selection of theories and models from cognitive science that explain how humans think; (3) a set of relational models that can be used to objectively judge the morality of different forms of human behavioural interactions. Overall, it appears that QBM tools may counter the deficits in natural human abilities to reason and solve problems, and that they may promote decision making practices that are moral and that the resulting decisions, themselves, may be moral

Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review