Tracking granules at the Sun's surface and reconstructing velocity fields. II. Error analysis

The determination of horizontal velocity fields at the solar surface is crucial to understanding the dynamics and magnetism of the convection zone of the sun. These measurements can be done by tracking granules. Tracking granules from ground-based observations, however, suffers from the Earth's atmospheric turbulence, which induces image distortion. The focus of this paper is to evaluate the influence of this noise on the maps of velocity fields. We use the coherent structure tracking algorithm developed recently and apply it to two independent series of images that contain the same solar signal. We first show that a k-\omega filtering of the times series of images is highly recommended as a pre-processing to decrease the noise, while, in contrast, using destretching should be avoided. We also demonstrate that the lifetime of granules has a strong influence on the error bars of velocities and that a threshold on the lifetime should be imposed to minimize errors. Finally, although solar flow patterns are easily recognizable and image quality is very good, it turns out that a time sampling of two images every 21 s is not frequent enough, since image distortion still pollutes velocity fields at a 30% level on the 2500 km scale, i.e. the scale on which granules start to behave like passive scalars. The coherent structure tracking algorithm is a useful tool for noise control on the measurement of surface horizontal solar velocity fields when at least two independent series are available.Comment: in press in Astronomy and Astrophysics, 9 page

A Proposal for a Tourism Regionalization of Poland Based on the Highest Levels of Tourism in a Region

The paper presents a brief review of twenty proposals for tourism regionalization of either a part of or the whole of Poland (or attempts to delimit the most attractive areas in terms of leisure), formulated between 1938 and 2012. It also analyses selected definitions of tourism regions and discusses the indicators which are proposed for the delimitation of tourism regions. Moreover, the paper attempts to indicate areas with the highest levels of tourism, in part modelled on Maria Mileska (1908-1988). It includes academic (precise) criteria for the designation of tourism regions. Some researchers’ comment that Mileska’s work is (partially) outmoded not so much from the methods employed as in the number of tourism regions and the areas covered. This should be regarded as understandable given that this regionalization was formulated at the beginning of the 1960s. Another important issue raised is the most recent tourism regionalization of Poland as prepared by Durydiwka

Fisher v. UT Austin - Contextualized Brief

Contextualization of the 2013 Supreme Court case, Fisher v. University of Texas at Austin, in which Abigail Fisher was denied admission. This paper also analyzes past Court cases dealing with affirmative action in the admissions process

Assessing Reconstruction: Did the South Undergo Revolutionary Change?

With the end of the Civil War, came a number of unanswered questions Reconstruction would attempt to answer for the South. While the South underwent economic, political and social changes for a short period, old traditions continued to persist resulting in racist sentiment

Fertility in Austria: An Overview

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Overview Chapter 6: The diverse faces of the Second Demographic Transition in Europe

This chapter discusses the concept of the second demographic transition (SDT) and its relevance for explaining the ongoing changes in family and fertility patterns across Europe. It takes a closer look at the shifts in values and attitudes related to family, reproduction, and children, and their representation in different chapters in this collection. It re-examines the link between the second demographic transition and fertility, highlights its strong positive association with fertility at later childbearing ages, and suggests that the transition does not necessarily lead to sub-replacement fertility levels. Subsequently, it provides an extensive discussion on the progression of the SDT behind the former ‘Iron Curtain.’ To explain some apparent contradictions in this process, it employs a conceptual model of ‘readiness, willingness, and ability’ (RWA) advocated by Lesthaeghe and Vanderhoeft (2001). It also explores the multifaceted nature of the second demographic transition between different social groups, and points out an apparent paradox: whereas lower-educated individuals often embrace values that can be characterised as rather traditional, they also frequently manifest family behaviour associated with the transition, such as non-marital childbearing, high partnership instability, and high prevalence of long-term cohabitation. This suggests that there may be two different pathways of the progression of the second demographic transition. The concluding section points out the role of structural constraints for the diffusion of the transition among disadvantaged social strata, highlights the importance of the ‘gender revolution’ for the SDT trends, and discusses the usefulness of the SDT framework.Europe, family, family change, fertility, second demographic transition, values

Overview Chapter 7: The rising importance of migrants for childbearing in Europe

This contribution looks at the influence of immigration on childbearing trends in the countries of Western, Northern and Southern Europe, which have received relatively large numbers of immigrants during the last decades. It analyses the contribution of migrants to the total number of births and compares fertility rates of migrant women with the fertility rates of native women, pointing out huge diversity between migrant groups. It also discusses the evidence regarding the progressive ‘assimilation’ in migrants’ fertility to the local fertility patterns and analyses the net impact of migrants on period fertility rates. This review reveals that migrant women typically retain substantially higher levels of period fertility than the ‘native’ populations, but this difference typically diminishes over time and with the duration of their stay in a country. Immigrants contribute substantially to the total number of births and their share of total births has increased in the last decade, exceeding in some countries one fifth of the recorded live births. However, the ‘net effect’ of the higher fertility of migrants on the period total fertility of particular countries remains relatively small, typically between 0.05 and 0.10 in absolute terms.childbearing, Europe, fertility, migration

Morphology and evolution of umbral dots and their substructures

Substructures - dark lanes and tails - of umbral dots (UDs) were predicted by numerical simulations of magnetoconvection. We analyse a 6 h 23 min time series of broadband images of a large umbra in the active region NOAA 10634, acquired with the 1-m Swedish Solar Telescope, in the wavelength band around 602 nm. A 43 min part of this series was reconstructed with the MFBD method, reaching a spatial resolution of 0.14". We measure brightness, size, lifetime, and horizontal velocities of various umbral structures. Most (90 %) of UDs and bright point-like features in faint LBs split and merge, and their median lifetimes are 3.5 or 5.7 min, depending on whether the split or merge event is considered as the end of their life. Both UDs and features in faint LBs that do not split or merge are clearly smaller (0.15") than the average size (0.17") of all features. Horizontal motions of umbral bright small-scale features are directed either into the umbra or along faint LBs with mean horizontal velocities of 0.34 km/s. Features faster than 0.4 km/s appear mostly at the periphery of the umbra. The intensity of dark lanes, measured in four bright central UDs (CUDs), is by a factor 0.8 lower than the peak intensity of CUDs. The width of dark lanes is probably less than the resolution limit 0.14". The characteristic time of substructure changes of UDs is ~4 min. We observe narrow (0.14") bright and dark filaments connected with PUDs. Usually one dark and two bright filaments form a 0.4" wide tail attached to one PUD, resembling a short dark-cored penumbral filament. Our results indicate the similarity between PUDs and PGs located at the tips of bright penumbral filaments. The features seen in numerical MHD simulations are consistent with our observations of dark lanes in CUDs and tails attached to PUDs.Comment: 8 pages, 8 figures, Astronomy & Astrophysics, in pres

Characteristic Dependence of Umbral Dots on their Magnetic Structure

Umbral dots (UDs) were observed in a stable sunspot in NOAA 10944 by the Hinode Solar Optical Telescope on 2007 March 1. The observation program consisted of blue continuum images and spectropolarimetric profiles of Fe I 630 nm line. An automatic detection algorithm for UDs was applied to the 2-hour continuous blue continuum images, and using the obtained data, the lifetime, size, and proper motion of UDs were calculated. The magnetic structure of the sunspot was derived through the inversion of the spectropolarimetric profiles. We calculated the correlations between UD's parameters (size, lifetime, occurrence rate, proper motion) and magnetic fields (field strength, inclination, azimuth), and obtained the following results: (1) Both the lifetime and size of UDs are almost constant regardless of the magnetic field strength at their emergence site. (2) The speed of UDs increases as the field inclination angle at their emergence site gets larger. (3) The direction of movement of UDs is nearly parallel to the direction of the horizontal component of magnetic field in the region with strongly inclined field, while UDs in the region with weakly inclined field show virtually no proper motion. Our results describe the basic properties of magnetoconvection in sunspots. We will discuss our results in comparison to recent MHD simulations by Schussler & Vogler (2006) and Rempel et al. (2009).Comment: 22 pages, 10 figures, accepted for publication in Ap