bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are there Forms of Sensible Qualities in Plato?
Authors: LARSEN PETER D. 
Published: November 2018

AbstractThis paper addresses the question of whether, according to Plato, there are forms of sensible qualities; it is also addressed to the wider question of whether there are forms of physical and material things more generally. In particular, it considers the tension raised by the following theses: (1) a Platonic form is the essence of some thing; (2) for Plato those essences that are forms are imperceptible and are knowable through reasoning alone; (3) knowing the essence of a particular color (e.g., red) requires presentation with the relevant perceptible quality and hence requires sense perception; and (4) if a sense perceptible quality has an essence, then that essence is a form. The solution I defend to this puzzle basically consists of accepting theses (1) through (3) but denying thesis (4). Sensible qualities, according to Plato, do have essences, but specifying their essences does not require that one postulate a separate form.
Benjamin’s gravity current into an ambient fluid with an open surface in a channel of general cross-section
Authors: Ungarish Marius 
Published: November 2018

We present the solution of the idealized steady-state gravity current of height $h$ and density $\unicode[STIX]{x1D70C}_{1}$ that propagates into an ambient motionless fluid of height $H$ and density $\unicode[STIX]{x1D70C}_{2}$ in a channel of general non-rectangular cross-section, with an upper surface open to the atmosphere, at high Reynolds number. The current propagates with speed $U$ and causes a depth decrease $\unicode[STIX]{x1D712}$ of the top surface. This is a significant extension of Benjamin’s (J. Fluid Mech., vol. 31, 1968, pp. 209–248) seminal solution for the gravity current in a rectangular (or laterally unbounded) channel with a fixed top ($\unicode[STIX]{x1D712}=0$). The determination of $\unicode[STIX]{x1D712}$ is a part of the problem. Supposing that the direction of propagation is $x$ and gravity acceleration $g$ acts in the $-z$ direction, the sidewalls are specified by $y=-f_{I}(z)$ and $y=f_{II}(z),~z\in [0.H]$, and the width is $f(z)=f_{I}(z)+\,f_{II}(z)$. The dimensionless parameters of the problem are $a=h/H\in (0,1)$ and $r=\unicode[STIX]{x1D70C}_{2}/\unicode[STIX]{x1D70C}_{1}\in (0,1)$. We show that a control-volume analysis of the type used by Benjamin produces a system of algebraic equations for $\tilde{\unicode[STIX]{x1D712}}=\unicode[STIX]{x1D712}/H$ and $Fr=U/(g^{\prime }h)^{1/2}$ as functions of $a$ and $r$, where $g^{\prime }=(r^{-1}-1)g$ is the reduced gravity. The geometry enters the equation via the width function $f(z)$. We present solutions for typical $f(z)$: rectangle, semi-circle, $\vee$ triangle and trapezoid $\text{}\underline{/~\backslash }$ . The results are physically acceptable and insightful. The non-negative dissipation condition defines the domain of validity $a\leqslant a_{max}(r)$ (also depending on $f(z)$); the equality sign corresponds to energy-conserving cases. The critical speed limitation (with respect to the characteristics) is also considered briefly and suggests a slightly smaller $a\leqslant a_{crit}(r)$. The open-top results in the Boussinesq limit $r\rightarrow 1$ coincide with the fixed-top solution. Upon the reduction of $r$, for a fixed thickness $a$, the value of $Fr$ decreases and $\unicode[STIX]{x1D712}$ increases, until the point of energy-conserving (non-dissipative) flow; for smaller $r$, a negative non-physical dissipation appears. The trends are more pronounced for a converging cross-section geometry (like $\text{}\underline{/~\backslash }$ ) than for the opposite shape (like $\vee$ triangle). The previously investigated Benjamin-type steady-state $Fr$ and dissipation results are particular cases of the new formulation: $f(z)=$ const. reproduces the two-dimensional results, and $\unicode[STIX]{x1D712}=0$ recovers the fixed-top solution.
On noise generation in low Reynolds number temporal round jets at a Mach number of 0.9
Authors: Bogey Christophe 
Published: November 2018

Two temporally developing isothermal round jets at a Mach number of 0.9 and Reynolds numbers of 3125 and 12 500 are simulated in order to investigate noise generation in high-subsonic jet flows. Snapshots and statistical properties of the flow and sound fields, including mean, root-mean-square and skewness values, spectra and auto- and cross-correlations of velocity and pressure, are presented. The jet at a Reynolds number of 12 500 develops more rapidly, exhibits more fine turbulent scales and generates more high-frequency acoustic waves than the other. In both cases, however, when the jet potential core closes, mixing-layer turbulent structures intermittently intrude on the jet axis and strong low-frequency acoustic waves are emitted in the downstream direction. These waves are dominated by the axisymmetric mode and are significantly correlated with centreline flow fluctuations. These results are similar to those obtained at the end of the potential core of spatially developing jets. They suggest that the mechanism responsible for the downstream noise component of these jets also occurs in temporal jets, regardless of the Reynolds number. This mechanism is revealed by averaging the flow and pressure fields of the present jets using a sample synchronization with the minimum values of centreline velocity at potential-core closing. A spot characterized by a lower velocity and a higher level of vorticity relative to the background flow field is found to develop in the interfacial region between the mixing layer and the potential core, to strengthen rapidly and reach a peak intensity when arriving on the jet axis, and then to break down. This is accompanied by the growth and decay of a hydrodynamic pressure wave, propagating at a velocity which, initially, is close to 65 per cent of the jet velocity and slightly increases, but quickly decreases after the collapse of the high-vorticity spot in the flow. During that process, sound waves are radiated in the downstream direction.
Phenology of the sugar beet weevil,Bothynoderes punctiventrisGermar (Coleoptera: Curculionidae), in Croatia
Authors: Drmić Z. , Čačija M. , Virić Gašparić H. , Lemić D. , Bažok R. 
Published: November 2018

AbstractThe sugar beet weevil (SBW),Bothynoderes punctiventrisGermar, 1824, is a significant pest in most of Eastern Europe. Here, the SBW is described and its seasonal activity characterized, in terms of its different developmental stages in relation to Julian days (JDs), degree-day accumulations (DDAs), and precipitation, as a key to improving monitoring and forecasting of the pest. The phenology and population characteristics of SBW were investigated in sugar beet fields in eastern Croatia over a 4-year period (2012–2015). By using the degree-day model (lower development threshold of 5°C, no upper development threshold, biofix 1 January), the first emergence of overwintering adults was determined as becoming established when the DDA reached 20. The adult emergence was completed when the DDA reached 428. SBW males emerged first, following which the females dominated the adult population. Overwintering adults were present in the field until early July. In August, adults of the offspring generation began to appear. The eggs laid by the overwintering generation required, on average, 10–15 days to develop into larvae; however, eggs were found in soil samples over a period of 102 days (between JDs 112 and 214). Larvae were present in the soil samples over a period of a maximum of 143 days (the first larvae were established on JD 122 and the last one on JD 265), and pupae were established in the soil over a period of 102 days (between JDs 143 and 245). This study provides important data for understanding SBW population dynamics and developing potential population dynamic models for pest forecasting on a regional scale.
The long-term variation of the effective magnetic field of the active star ε Eridani
Authors: Scalia Cesare , Leone Francesco , Gangi Manuele 
Published: November 2018

AbstractLong-term periodicities of magnetic fields in cool stars are usually studied from activity indicators, which are only indirectly related to the presence of the field. Direct detections are complicated issues since even a complex magnetic structure, as the solar one, has a very low disk integrated magnetic signal, which is usually hidden in the noise level. We introduce a method for the direct measurement of small integrated longitudinal stellar magnetic fields (effective magnetic fields), called multi-line slope method, based on the regression of the Stokes V signal with respect to the first derivative of Stokes I. We present the results of the application of this technique to a dataset of 9 yr of observations of the active star epsilon Eridani, obtained with the spectropolarimeters Narval, HARPSpol and CAOS, showing that the long-term variation of the effective magnetic field corresponds to the period of the cycle retrieved by the activity indicators.
Flux tube model in the solar atmosphere
Authors: Sen S. , Mangalam A. 
Published: November 2018

AbstractWe construct two classes of the magnetohydrostatic equilibria of the axisymmetric flux tubes with twisted magnetic fields in the stratified solar atmosphere that span from the photosphere to the transition region. We built the models by incorporating specific forms of the gas pressure and poloidal current in the Grad-Shafranov equation. This model gives both closed and open field structure of the flux tube. The other open field model we construct is based on the self-similar formulation, where we have incorporated specific forms of the gas pressure, poloidal current and two different shape functions. We study the homology of the parameter space that is consistent with the solar atmosphere and find that the estimation of the magnetic structure inside the flux tubes is consistent with the observation and simulation results of the magnetic bright points.
Solar-Cycle variation in the photospheric mean velocity flows: GONG observations
Authors: Kumar Brajesh 
Published: November 2018

AbstractThe solar oscillation frequencies have shown variation over the solar activity cycle, which is believed to be the indicator of the structural and magnetic changes taking place in the Sun. The ground-based network of six identical solar telescopes in the Global Oscillation Network Group (GONG) program has been nearly-continuously observing the Sun since the last quarter of the year 1995 for Doppler imaging of the solar-disk aimed to study the oscillations and velocity flows on the surface of the Sun. In this work, we study the variations in the solar disk-integrated mean velocity flows on the solar surface as observed with the GONG over the complete Solar Cycle 23 and ongoing Cycle 24. The correlation analysis of these solar photospheric mean velocity flows relative to the various solar activity indicators is also discussed.
Magnetic field topology from non-force free extrapolation and magnetohydrodynamic simulation of its eventual dynamics
Authors: Nayak Sushree S. , Bhattacharyya R. , Prasad A. , Hu Q. 
Published: November 2018

AbstractMagnetic reconnections (MRs) for various magnetic field line (MFL) topologies are believed to be the initiators of solar eruptive events like flares and coronal mass ejections (CMEs). Consequently, important is a thorough understanding and quantification of the MFL topology and their evolution which leads to MRs. Contemporary standard is to extrapolate the coronal MFLs using equilibrium models where the Lorentz force on the coronal plasma is zero everywhere. In tandem, a non-force-free-field (NFFF) extrapolation scheme has evolved and allows for a Lorentz force which is non-zero only at the photosphere but asymptotically vanishes with height. The paper reports magnetohydrodynamic (MHD)- simulations initiated by NFFF extrapolation of the coronal MFLs for a flare producing active region NOAA 11158. Interestingly, quasi-separatrix layers (QSLs) which facilitate MRs are detected in the extrapolated MFLs and, here the paper makes an attempt to asses the role of QSLs in the flare onsets.
Four years of starspot evolution on an active F-type ultra-fast rotator KIC 6791060
Authors: Karmakar Subhajeet , Pandey Jeewan C. , Savanov Igor S. , Raj Ashish , Dmitrienko E. S. , Pakhomov Yurij , Sahu D. K. 
Published: November 2018

AbstractUsing the data obtained fromKeplersatellite, we have analyzed an F-type ultra-fast rotator KIC 6791060. We derive a rotational period of 0.34365±0.00004 d. Multiple periodicity with a period separation of ~0.00016 d was detected, which appears to be a result of the relative velocity between the multiple spot-groups in different stellar latitudes due to the surface differential rotation. Modeling of the surface inhomogeneities using the light curve of 3899 epochs shows the evidence of single active longitude region. The active longitude is found to drift along the longitude at a rate similar to the detected period separation of the F-type star. The surface coverage of cool spots is found to be in the range of ~0.07–0.44%. The low value of the spottedness can be interpreted probably due to the thinner convection zone on the F-type star.
Study of Long-Term Variations in Hemispheric Asymmetry of Solar Activity
Authors: Ravindra B. , Javaraiah J. 
Published: November 2018

AbstractSunspot activity exhibits hemispheric asymmetry. We study the long-term variations in the hemispheric sunspot area from Kodaikanal white-light data during 1921 – 2011. The results on the presence or absence of double peak in an individual solar cycle, dominant hemispheric activity, and phase lag between the activities of northern and southern hemispheres, etc., are presented.
The State of the Solar Wind, Magnetosphere, and Ionosphere During the Maunder Minimum
Authors: Riley Pete , Lionello Roberto , Linker Jon A. , Owens Mathew J. 
Published: November 2018

AbstractBoth direct observations and reconstructions from various datasets, suggest that conditions were radically different during the Maunder Minimum (MM) than during the space era. Using an MHD model, we develop a set of feasible solutions to infer the properties of the solar wind during this interval. Additionally, we use these results to drive a global magnetospheric model. Finally, using the 2008/2009 solar minimum as an upper limit for MM conditions, we use results from the International Reference Ionosphere (ILI) model to speculate on the state of the ionosphere. The results describe interplanetary, magnetospheric, and ionospheric conditions that were substantially different than today. For example: (1) the solar wind density and magnetic field strength were an order of magnitude lower; (2) the Earth’s magnetopause and shock standoff distances were a factor of two larger; and (3) the maximum electron density in the ionosphere was substantially lower.
Reassessing the Predictions of Sunspot Cycle 24
Authors: Bhatt Nipa J. , Jain Rajmal 
Published: November 2018

AbstractPredictions of sunspot cycle are important due to their space weather effects. Bhattet al.(2009) predicted sunspot cycle 24 (Maximum amplitude: 92.8±19.6; Timing:October 2012±4 months) using relative sunspot number (International Sunspot Number), and average geomagnetic activity indexaaconsidering 2008 as the year of sunspot minimum. Owing to the extended solar minimum till 2009, we re-examine our prediction model. Also, the newly calibrated international sunspot number reduces many discrepancies in the old dataset and is available from Solar Influences Data Center (SIDC) website. Considering 2009 as sunspot minimum year and newly calibrated international sunspot number, (i) The annual maximum amplitude of cycle 24 = 118.5±24.4 (observed = 113.3±0.1), (ii) A smoothed monthly mean sunspot number maximum in January 2014±4 months (observed in February 2014). Our prediction method appears to be a reliable indicator for the predictability of cycle 25.
Building a Large Solar Analog Sample Using K2
Authors: Buzasi Derek L. 
Published: November 2018

AbstractWe have begun a project aimed at providing a large consistent set of well- vetted solar analogs in order to address questions of stellar rotation, activity, dynamos, and gyrochronology. We make use of the K2 mission fields to obtain precise photometric time series, supplemented by ground-based photometric and spectroscopic data for promising candidates. From this data we will derive rotation periods, spot coverages, and flare rates for a well- defined and well-calibrated sample of solar analogs.
Ultraviolet Solar Spectral Irradiance Variation on Solar Cycle Timescales
Authors: Snow Martin , Eparvier Francis G. , Harder Jerald , Jones Andrew R. , McClintock William E. , Richard Erik , Woods Thomas N. 
Published: November 2018

AbstractUltraviolet (UV) Solar spectral Irradiance (SSI) has been measured from orbit on a regular basis since the beginning of the space age. These observations span four Solar Cycles, and they are crucial for our understanding of the Sun-Earth connection and space weather. SSI at these wavelengths are the main drivers for the upper atmosphere including the production and destruction of ozone in the stratosphere. The instruments that measure UV SSI not only require good preflight calibration, but also need a robust method to maintain that calibration on orbit. We will give an overview of the catalog of current and former UV SSI measurements along with the calibration philosophy of each instrument and an estimation of the uncertainties in the published irradiances.
Kyiv monitoring program of spectral line variations with the 11-year cycle
Authors: Shchukina Nataliia , Osipov Sergej , Kostyk Roman , Stodilka Myroslav 
Published: November 2018

AbstractKyiv program of monitoring of long-term variation of solar spectral lines at the horizontal solar telescope of the Main Astronomical Observatory of Ukraine is described. The aim of the program is to clarify the issue how the physical parameters of the quiet solar atmosphere change over the 11-year cycle of solar activity. The diagnostics of the atmospheric variation includes analysis of more than 40 spectral lines of neutral and ionized chemical elements observed at the solar disk and at the limb near north and south poles with high spectral resolution. The results of monitoring show that during 2012–2017 a line core depths and a line full widths at half maximum respond to the cycle modulation of the global unsigned magnetic field of the Sun. Such a correlation can be explained by assuming that temperature gradient of the solar photosphere is growing with solar activity.
Dynamo Processes Constrained by Solar and Stellar Observations
Authors: Weber Maria A. 
Published: November 2018

AbstractOur understanding of stellar dynamos has largely been driven by the phenomena we have observed of our own Sun. Yet, as we amass longer-term datasets for an increasing number of stars, it is clear that there is a wide variety of stellar behavior. Here we briefly review observed trends that place key constraints on the fundamental dynamo operation of solar-type stars to fully convective M dwarfs, including: starspot and sunspot patterns, various magnetism-rotation correlations, and mean field flows such as differential rotation and meridional circulation. We also comment on the current insight that simulations of dynamo action and flux emergence lend to our working knowledge of stellar dynamo theory. While the growing landscape of both observations and simulations of stellar magnetic activity work in tandem to decipher dynamo action, there are still many puzzles that we have yet to fully understand.
Study of Coronal Rotation using X-ray images observed by Hinode
Authors: Chandra Satish , Singh Vivek Kumar , Thomas Sanish 
Published: November 2018

AbstractSolar rotation is still one of the unresolved concern of solar physics. We performed time series analysis on the bins formed on equally separated latitude regions on the soft X-ray images. These images are observed with the X-ray telescope (XRT) on board the Hinode satellite. The flux modulation method traces the passage of X-ray feature over the solar disc and statistical analysis of the time series data of the SXR images (one per day) for the period extends from year 2015 to 2017 gives the coronal rotation period as a function of latitude. The investigation provided quite systematic information of the solar rotation and its variability.
Prediction of future evolution of solar cycle 24 using machine learning techniques
Authors: Gopinath Sumesh , Prince P. R. 
Published: November 2018

AbstractForecasting the solar activity is of great importance not only for its effect on the climate of the Earth but also on the telecommunications, power lines, space missions and satellite safety. In the present work, machine learning using Artificial Neural Networks (ANNs) called Nonlinear Autoregressive Network (NAR) with Exogenous Inputs (NARX) have been applied for the prediction of future evolution of the present sunspot cycle. NARX network is able to combine the performance of ANN algorithm with nonlinear autoregressive method to handle problems such as finding dependencies among solar indices and prediction of solar cycle evolution.
Sunspot data collection of Specola Solare Ticinese in Locarno
Authors: Ramelli Renzo , Cagnotti Marco , Cortesi Sergio , Bianda Michele , Manna Andrea 
Published: November 2018

AbstractSunspot observations and counting are carried out at the Specola Solare Ticinese in Locarno since 1957 when it was built as an external observing station of the Zurich observatory. When in 1980 the data center responsibility was transferred from ETH Zurich to the Royal Observatory of Belgium in Brussels, the observations in Locarno continued and Specola Solare Ticinese got the role of pilot station. The data collected at Specola cover now the last 6 solar cycles.The aim of this presentation is to discuss and give an overview about the Specola data collection, the applied counting method and the future archiving projects. The latter includes the publication of all data and drawings in digital form in collaboration with the ETH Zurich University Archives, where a parallel digitization project is ongoing for the document of the former Swiss Federal Observatory in Zurich collected since the time of Rudolph Wolf.
State-of-the-art of kinematic modeling the solar cycle
Authors: Jiang Jie 
Published: November 2018

AbstractThe kinematic modeling of the solar convection zone remains the workhorse of the solar dynamo to understand the solar cycle. During the past several years, the major progress in understanding the solar cycle using kinematic models is as follows. (1). The Babcock-Leighton (BL) mechanism was confirmed to be at the essence of the solar cycle. (2). The scatter of sunspot tilt angles is identified as a major cause of solar cycle irregularities. (3). The important roles of the magnetic pumping in the dynamo process are recognized. (4). Some 3D kinematic BL type dynamo models have been developed. As a key part of the solar dynamo loop, the surface observable part of the BL mechanism makes the physics-based solar cycle prediction feasible. Including the effects of the tilt scatter on the polar field generation, the possible strength of the subsequent cycle can be predicted when a cycle starts for a few years.
Un-interrupted Sun-as-a-star Helioseismic Observations over Multiple Solar Cycles
Authors: Jain Kiran , Tripathy Sushanta , Hill Frank , Salabert David , García Rafael A. , Broomhall Anne-Marie 
Published: November 2018

AbstractWe analyze Sun-as-a-star observations spanning over solar cycles 22 – 24 from the ground-based network BiSON and solar cycles 23 – 24 collected by the space-based VIRGO and GOLF instruments on board the SoHO satellite. Using simultaneous observations from all three instruments, our analysis suggests that the structural and magnetic changes responsible for modifying the frequencies remained comparable between cycle 23 and cycle 24 but differ from cycle 22. Thus we infer that the magnetic layer of the Sun has become thinner since the beginning of cycle 23 and continues during the current cycle.