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

Ultra-Low Fertility in Korea: The Role of Tempo Effect

Background: The total fertility rate (TFR) in South Korea has fallen below 1.3 since 2001. However, little is known about the role of the rapid shift towards late childbearing in driving Korean fertility decline to this “ultra-low” level. Objective: We provide an in-depth analysis of period fertility trends by birth order in South Korea from 1981 to 2014 when the period TFR fell from 2.66 to extreme low levels. Methods: We combine census and birth registration data to estimate period and cohort fertility indicators by birth order. We compare changes in conventional TFR with tempo- and parity-adjusted total fertility rate (TFRp*) and their birth order-specific components. Results: Tempo effect linked to the shift towards delayed childbearing has had a strong and persistent negative influence on period TFRs in Korea since the early 1980s. Without the shift to later childbearing, period fertility rates in Korea would consistently stay higher and would decline more gradually, falling below a threshold of very low fertility, 1.5, only in 2014. The postponement of childbearing and the resulting tempo effect were strongest in the early 2000s, when Korean TFR reached the lowest levels. More recently, Korean fertility has been characterized by diminishing tempo effect and falling first and second birth rates. This trend marks a break with the previous pattern of almost universal fertility and a strong two-child family model. Contribution: Our study demonstrates the importance of tempo effect in explaining the shift to “ultra-low” fertility in Korea and in East Asia

Misleading Policy Messages from the Period TFR: Should We Stop Using It?

Public discussions about fertility trends and policies in developed countries refer almost exclusively to the period Total Fertility Rate (TFR), which is commonly misinterpreted as the "mean number of children per woman" as if it were a cohort measure of fertility. We argue that the use of this indicator frequently leads to incorrect interpretations of period fertility levels and trends, resulting in distorted policy conclusions and, potentially, in misguided policies. We illustrate this point with four policy-relevant examples, drawn from contemporary Europe. These illustrations show that the TFR (a) inflates the presumed gap between fertility intentions and realised fertility, (b) erroneously suggests a significant fertility increase in many countries of Europe after the year 2000, (c) often exaggerates the level of immigrants' fertility and (d) frequently suggests that family-related policies which led to shorter birth spacing in fact brought an upward swing in fertility level. We argue that there seems to be no policy-relevant question for which the period TFR would be the indicator of choice to be preferred over other existing measures, which range from measures related to future cohort size (total number of births) to sophisticated fertility indexes controlling for age, parity, duration since previous birth and tempo effect. Hence, there is a strong case for stopping the use of the period TFR as a one-fits-all fertility indicator which is now common practice

Brightness, distribution, and evolution of sunspot umbral dots

We present a 106-minute TiO (705.7nm) time series of high spatial and temporal resolution that contains thousands of umbral dots (UDs) in a mature sunspot in the active region NOAA 10667 at $\mu$=0.95. The data were acquired with the 1-m Swedish Solar Telescope on La Palma. With the help of a multilevel tracking (MLT) algorithm the sizes, brightnesses, and trajectories of 12836 umbral dots were found and analyzed. The MLT allows UDs with very low contrast to be reliably identified. Inside the umbra we determine a UD filling factor of 11%. The histogram of UD lifetimes is monotonic, i.e. a UD does not have a typical lifetime. Three quarters of the UDs lived for less than 150s and showed no or little motion. The histogram of the UD diameters exhibits a maximum at 225km, i.e. most of the UDs are spatially resolved. UDs display a typical horizontal velocity of 420m/s and a typical peak intensity of 51% of the mean intensity of the quiet photosphere, making them on average 20% brighter than the local umbral background. Almost all mobile UDs (large birth-death distance) were born close to the umbra-penumbra boundary, move towards the umbral center, and are brighter than average. Notably bright and mobile UDs were also observed along a prominent UD chain, both ends of which are located at the umbra-penumbra boundary. Their motion started primarily at either of the ends of the chain, continued along the chain, and ended near the chain's center. We observed the splitting and merging of UDs and the temporal succession of both. For the first time the evolution of brightness, size, and horizontal speed of a typical UD could be determined in a statistically significant way. Considerable differences between the evolution of central and peripheral UDs are found, which point to a difference in origin

European Demographic Datasheet 2016

The European Demographic Datasheet 2016 shows key demographic data, population trends and projections until 2050. It covers fertility, mortality, migration and population structure, including population ageing, and their changes. The datasheet combines data for all countries of Europe and for broader European regions, as well as maps, population pyramids, tables, graphs and featured thematic boxes. It pays special attention to the importance of migration for the current and future population changes across the continent and to the alternative indicators of population ageing. In comparison to the Data Sheet Poster, the online version provides expanded data coverage, additional maps and population pyramids, ranking charts and details about data sources and definitions. It also allows users to download all data and images

Religiosity and Spatial Demographic Differences in the Netherlands

This paper investigates whether current differences in religiosity between the Dutch regions are also manifested in spatial demographic patterns. We use cluster analysis to distinguish relatively homogeneous clusters of regions, specified by religious affiliation and the frequency of churchgoing among their populations. Although the regional demographic differences are relatively modest in the Netherlands, between-clusters contrasts are consistent with the expected influence of religiosity. The cluster including the most conservative region, the so-called Bible Belt, also displays the most traditional demographic patterns. In order to differentiate the impact of religiosity from the social and economic factors, we perform stepwise regression of selected indicators of fertility, union formation and living arrangements. The frequency of churchgoing rather than the fact of belonging to a certain denomination manifested the strongest impact on the regional demographic contrasts. In case of fertility of parity four and higher, marriage rate and the proportion of young women cohabiting, churchgoing turned out to be the most important predictor of regional differentiation

Misleading policy messages derived from the period TFR: Should we stop using it?

Discussions about fertility in developed countries refer almost exclusively to the period Total Fertility Rate (TFR). We argue that the use of this indicator frequently leads to incorrect interpretation of period fertility levels and trends, resulting in distorted policy conclusions and, potentially, in misguided policies. We illustrate this with four policy-relevant examples, drawn from contemporary Europe. These illustrations show that the TFR (a) inflates the presumed gap between fertility intentions and realised fertility, (b) erroneously suggests a significant fertility increase in many countries of Europe after the year 2000, (c) often exaggerates the level of immigrants fertility and (d) frequently suggests that family-related policies which led to shorter birth spacing in fact brought an upward swing in fertility level. There seems to be no policy-relevant question for which the period TFR would be the indicator of choice to be preferred over other existing measures

Age, gender and COVID-19 infections

Data for ten European countries which provide detailed distribution of COVID-19 cases by sex and age show that among people of working age, women diagnosed with COVID-19 substantially outnumber infected men. This pattern reverses around retirement: infection rates among women fall at age 60-69, resulting in a cross-over with infection rates among men. The relative disadvantage of women peaks at ages 20-29, whereas the male disadvantage in infection rates peaks at ages 70-79. The elevated infection rates among women of working age are likely tied to their higher share in health- and care-related occupations. Our examination also suggests a link between women's employment profiles and infection rates in prime working ages. The same factors that determine women's higher life expectancy account for their lower fatality and higher male disadvantage at older ages