Variation of the solar diameter from solar eclipse observations, 1715–1991

The diameter of the Sun may be measured at the time of a solar eclipse. We have performed an exhaustive search of the astronomical literature to find all existing observations of solar eclipses suitable for this purpose. We have also taken new observations by new techniques. We have undertaken a project to reduce them systematically, and in an automated, self-consistent way. This will produce determinations of the solar radius at the times of solar eclipses from 1715 to the present. Re-reduction, using newer ephemerides, of observations made in 1984 shows that the component of the residuals caused by the ephemeris is substantially reduced. This paper summarizes the research plan, outlines the detailed astronomical features included in the calculations, and presents the results available.     

Korean East Coast wave predictions by means of ensemble Kalman filter data assimilation

To respond to the need for preventing offshore and coastal accidents, damage and flooding, a state-of-the-art coastal wave forecast system for the East Coast of Korea waters is being developed. Given that the quality of the input wind has been identified as the main factor influencing the quality of the wave results, the effectiveness of adjusting the wind fields by means of data assimilation using the ensemble Kalman filter technique has been explored. In this article the model setup, the data assimilation parameters and the validation of the predictions during stormy periods is described. The validation shows that the model is able to provide predictions of coastal waves fulfilling available benchmarks; especially, the data assimilation analysis and forecast predictions are judged to be of high quality.     

Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation

The orbital structure of trans-neptunian objects (TNOs) in the trans-neptunian belt (Edgeworth-Kuiper belt) and scattered disk provides important clues to understand the origin and evolution of the Solar System. To better characterize these populations, we performed computer simulations of currently observed objects using long-arc orbits and several thousands of clones. Our preliminary analysis identified 622 TNOs, and 65 non-resonant objects whose orbits penetrate that of at least one of the giant planets within 1 Myr (the centaurs). In addition, we identified 196 TNOs locked in resonances with Neptune, which, sorted by distance from the Sun, are 1:1 (Neptune trojans), 5:4, 4:3, 11:8, 3:2, 18:11, 5:3, 12:7, 19:11, 7:4, 9:5, 11:6, 2:1, 9:4, 16:7, 7:3, 12:5, 5:2, 8:3, 3:1, 4:1, 11:2, and 27:4. Kozai resonant TNOs are found inside the 3:2, 5:3, 7:4, and 2:1 resonances. We present detailed general features for the resonant populations (i.e., libration amplitude angles, libration centers, Kozai libration amplitudes, etc.). Taking together the simulations of Lykawka and Mukai [Lykawka, P.S., Mukai, T., 2007. Icarus 186, 331-341], an improved classification scheme is presented revealing five main classes: centaurs, resonant, scattered, detached and classical TNOs. Scattered and detached TNOs (non-resonant) have q (perihelion distance) <37 AU and q>40 AU, respectively. TNOs with 37 AU<q<40 AU occupy an intermediate region where both classes coexist. Thus, there are no clear boundaries between the scattered and detached regions. We also securely identified a total of 9 detached TNOs by using 4-5 Gyr orbital integrations. Classical objects are non-resonant TNOs usually divided into cold and hot populations. Their boundaries are as follows: cold classical TNOs (i?5°) are located at 37 AU<a<40 AU (q>37 AU) and 42 AU<a<47.5 AU (q>38 AU), and hot classical TNOs (i>5°) occupy orbits with 37 AU<a<47.5 AU (q>37 AU). However, a more firm classification is found with i>10° for hot classical TNOs. Lastly, we discuss some implications of our classification scheme comparing all TNOs with our model and other past models.     

Geo-scape,a granularity depended spatialization tool for visualizing multidimensional data sets

Recently, the expertise accumulated in the field of geovisualization has found application in the visualization of abstract multidimensional data, on the basis of methods called spatialization methods. Spatialization methods aim at visualizing multidimensional data into low-dimensional representational spaces by making use of spatial metaphors and applying dimension reduction techniques. Spatial metaphors are able to provide a metaphoric framework for the visualization of information at different levels of granularity. The present paper makes an investigation on how the issue of granularity is handled in the context of representative examples of spatialization methods. Furthermore, this paper introduces the prototyping tool Geo-Scape, which provides an interactive spatialization environment for representing and exploring multidimensional data at different levels of granularity, by making use of a kernel density estimation technique and on the landscape “smoothness” metaphor. A demonstration scenario is presented next to show how Geo-Scape helps to discover knowledge into a large set of data, by grouping them into meaningful clusters on the basis of a similarity measure and organizing them at different levels of granularity.     

From subsurface to surface: a multidisciplinary approach to decoding uplift histories in tectonically-active karst landscapes

We present an integrated study of subsurface and surficial karst landforms to unravel the uplift history of karst landscape in a tectonically-active area. To this end, we apply a multidisciplinary approach by combining cave geomorphology and Th/U dating of speleothems with remote sensing plus geophysical imaging of surface landforms. We use as an example Mt. Menikio in northern Greece where four caves share well-defined epiphreatic/shallow phreatic characteristics that are related to the distribution of surface and buried doline fields and provide evidence for three distinct water table stillstands (e.g. expressed as cave levels) now lying at ~130 m, ~800 m and ~1600 m a.m.s.l. Our dating constraints delimit the age of the lower water table stillstand prior to 77 ka ago and imply a maximum rate of relative base level drop of 0.45 mma^-1, which is consistent with relative tectonic uplift rate estimates along currently active normal faults. We interpret the elevation of the higher water table stillstands to reflect earlier phases of uplift related to the regional tectonic events associated with the development of the North Anatolian Fault and the Northern Aegean area. Our analysis shows that the combined study of epiphreatic/shallow phreatic caves and surficial karst landforms together, is a robust way to investigate the uplift history of a karst landscape in a tectonically-active setting. © 2019 John Wiley & Sons, Ltd.     

Bank erosion in agricultural drainage networks: new challenges from structure‐from‐motion photogrammetry for post‐event analysis

Drainage channels are an integral part of agricultural landscapes, and their impact on catchment hydrology is strongly recognized. In cultivated and urbanized floodplains, channels have always played a key role in flood protection, land reclamation, and irrigation. Bank erosion is a critical issue in channels. Neglecting this process, especially during flood events, can result in underestimation of the risk in flood‐prone areas. The main aim of this work is to consider a low‐cost methodology for the analysis of bank erosion in agricultural drainage networks, and in particular for the estimation of the volumes of eroded and deposited material. A case study located in the Veneto floodplain was selected. The research is based on high‐resolution topographic data obtained by an emerging low‐cost photogrammetric method (structure‐from‐motion or SfM), and results are compared to terrestrial laser scanning (TLS) data. For the SfM analysis, extensive photosets were obtained using two standalone reflex digital cameras and an iPhone5® built‐in camera. Three digital elevation models (DEMs) were extracted at the resolution of 0.1 m using SfM and were compared with the ones derived by TLS. Using the different DEMs, the eroded areas were then identified using a feature extraction technique based on the topographic parameter Roughness Index (RI). DEMs derived from SfM were effective for both detecting erosion areas and estimating quantitatively the deposition and erosion volumes. Our results underlined how smartphones with high‐resolution built‐in cameras can be competitive instruments for obtaining suitable data for topography analysis and Earth surface monitoring. This methodology could be potentially very useful for farmers and/or technicians for post‐event field surveys to support flood risk management. Copyright © 2015 John Wiley & Sons, Ltd.     

Origin of scattered disk resonant TNOs: Evidence for an ancient excited Kuiper belt of 50 AU radius

Resonance occupation of trans-neptunian objects (TNOs) in the scattered disk (>48 AU) was investigated by integrating the orbits of 85 observed members for 4 Gyr. Twenty seven TNOs were locked in the 9:4, 16:7, 7:3, 12:5, 5:2, 8:3, 3:1, 4:1, 11:2, and 27:4 resonances. We then explored mechanisms for the origin of the resonant structure in the scattered disk, in particular the long-term 9:4, 5:2, and 8:3 resonant TNOs (median 4 Gyr), by performing large scale simulations involving Neptune scattering and planetary migration over an initially excited planetesimals disk (wide range of eccentricities and inclinations). To explain the formation of Gyr-resident populations in such distant resonances, our results suggest the existence of a primordial planetesimal disk of at least 45-50 AU radius that suffered a dynamical perturbation leading to 0.1-0.3 or greater eccentricities and a range of inclinations up to ∼20° during early stages of the Solar System history, before planetary migration.     

HABIT PLANES OF PLATELIKE SCHREIBERSITE IN HEXAHEDRITES*

We have measured the habit planes of plate rhabdites [(Fe, Ni)₃P] with respect to the parent kamacite phase (α, Fe-Ni) in eight hexahedrites. This was accomplished using x-ray diffraction plus two-surface trace analysis. Results show that plate rhabdites form on either {001} or {122} planes in the parent kamacite. The meteorite Uwet exhibits a {112} habit plane which is possibly an anomaly due to the occurrence of a large shock event during rhabdite nucleation (～ 550–650 °C).