The Role of Subsurface Flows in Solar Surface Convection: Modeling the Spectrum of Supergranular and Larger Scale Flows

We model the solar horizontal velocity power spectrum at scales larger than granulation using a two-component approximation to the mass continuity equation. The model takes four times the density scale height as the integral (driving) scale of the vertical motions at each depth. Scales larger than this decay with height from the deeper layers. Those smaller are assumed to follow a Kolomogorov turbulent cascade, with the total power in the vertical convective motions matching that required to transport the solar luminosity in a mixing length formulation. These model components are validated using large scale radiative hydrodynamic simulations. We reach two primary conclusions: 1. The model predicts significantly more power at low wavenumbers than is observed in the solar photospheric horizontal velocity spectrum. 2. Ionization plays a minor role in shaping the observed solar velocity spectrum by reducing convective amplitudes in the regions of partial helium ionization. The excess low wavenumber power is also seen in the fully nonlinear three-dimensional radiative hydrodynamic simulations employing a realistic equation of state. This adds to other recent evidence suggesting that the amplitudes of large scale convective motions in the Sun are significantly lower than expected. Employing the same feature tracking algorithm used with observational data on the simulation output, we show that the observed low wavenumber power can be reproduced in hydrodynamic models if the amplitudes of large scale modes in the deep layers are artificially reduced. Since the large scale modes have reduced amplitudes, modes on the scale of supergranulation and smaller remain important to convective heat flux even in the deep layers, suggesting that small scale convective correlations are maintained through the bulk of the solar convection zone.Comment: 36 pages, 6 figure

National Autism Indicators Report: Vocational Rehabilitation 2016

Employment is about more than simply earning a paycheck - it influences quality of life, independence, and wellness. Historically, employment outcomes for adults with autism are poor. The U.S. Vocational Rehabilitation system (VR) is designed to provide support to states for implementation of services to assist people with disabilities to prepare for, find, and keep employment. VR data allow us to examine some outcomes for those with autism compared to their peers.To make a difference, research must reach those who need it. The National Autism Indicators Report series presents our research findings in a clearly communicated, open-access, online format to speed the delivery of information to decision-makers while maintaining very high standards of scientific credibility

Expansion of the Supergranular Magnetic Network through the Solar Atmosphere

The solar magnetic field has its footpoints in the photosphere, extends through the chromosphere, and is thought to expand through the transition region and into the corona. It is organized by fluid motions to form strong flux concentrations within the boundaries of the supergranular convection cells. These boundaries are the network lanes observed in line emission, and they display increasing width with height through the solar atmosphere. The network field concentrations are surrounded by a mixed-polarity internetwork magnetic field on the scale of granulation. We use a potential magnetic field extrapolation of synthetic photospheric magnetograms to study the magnetic network topology and the effects of a mixed-polarity background field on the network expansion with height through the solar atmosphere.We find that the expansion of the network boundary with height deviates significantly from the funnel expansion model. Moreover, we find that the background magnetic field has a considerable effect on the filling factor of the network area with height, even though the background flux is strictly equal to zero

Peaks and Troughs in Helioseismology: The Power Spectrum of Solar Oscillations

I present a matched-wave asymptotic analysis of the driving of solar oscillations by a general localised source. The analysis provides a simple mathematical description of the asymmetric peaks in the power spectrum in terms of the relative locations of eigenmodes and troughs in the spectral response. It is suggested that the difference in measured phase function between the modes and the troughs in the spectrum will provide a key diagnostic of the source of the oscillations. I also suggest a form for the asymmetric line profiles to be used in the fitting of solar power spectra. Finally I present a comparison between the numerical and asymptotic descriptions of the oscillations. The numerical results bear out the qualitative features suggested by the asymptotic analysis but suggest that numerical calculations of the locations of the troughs will be necessary for a quantitative comparison with the observations.Comment: 18 pages + 8 separate figures. To appear in Ap

Correlations and fault systematics in the Passamaquoddy Bay area, Southwestern New Brunswick

Three distinct fault-bounded litho-tectonic units have been recognized on Campobello Island in southern Passamaquoddy Bay. These units are the Upper Silurian Wilsons Beach beds, the Lower Silurian Quoddy Formation and the Upper Precambrian Coldbrook Group. Contact relationships between these units and their correlations in the Passamaquoddy Bay area resolve correlation problems between coastal Maine and New Brunswick, and demonstrate the nature of the junction between the Avalon Platform and the Acadian mobile belt. The Wilsons Beach beds are a remnant of the Acadian belt on northeastern Campobello Island, whereas the Coldbrook Group and the Quoddy Formation represent a fault block of the Avalon Platform. The Coldbrook Group, probably overlain unconformably by the Quoddy Formation, plunges to the southwest beneadi the Quoddy Formation of southeastern Maine. The Siluro-Devonian basins formed in a tensional tectonic regime in response to normal(?) faulting. These faults formed along pre-existing zones of crustal weakness that were generated during the late Precambrian by major strike-slip faulting. The present geological configuration of the area was basically established by episodic reactivation of northeast-trending faults (high-angle reverse movements) during the compressional regime of the Acadian Orogeny, RÉSUMÉ On reconnait trois unités litho-techniques bordérs par des failles sur l'ile de Campobello dans le sud de la baie-de Passamaquoddy. Ce sont les lits de Wilson Beach (Silurien supérieur), la Formation de Quoddy (Silurien inférieur) et le Groupe de Coldbrook (Précambrien supérieur). La corrélation de ces unités et de leurs contacts dans la baie de Passamaquoddy résout les problèmes de corrélation entre la côte du Maine et le Nouveau-Brunswick et démontre la nature de la jonction entie la Plate-Forme d'Avalon et la ceinture mobile acadienne. Les lits de Wilson Beach sont un residu de la ceinture acadienne sur le nord-cst de l'ile de Campobello. Par contre, le Groupe de Coldbrook et la Formation de Quoddy représentent un bloc faillé de la Plate-Forme d'Avalon. Le Groupe de Coldbrook est probablement recouvert avec discordance par la Formation de Quoddy et plonge vers le sud-ouest sous la Formation de Quoddy dans le sud-est du Maine. Les bassins siluro-dévoniens se formèrent dans un régime tectonique de tension en résponse à un mouvement normal(?) de failles. Ces failles se créerent le long de zones de faiblcsse crustale déjà établies et issues d'un important coulissement tardi-précambrien. La configuration géologique actuelle de la région s'établit principalement par réactivation épisodique de failles à tendance nord-est (mouvements inverses à fort pendage) durant le régime compressif de l'orogénèse acadienne, [Traduit par le journal

The Intensity Profile of the Solar Supergranulation

We have measured the average radial (cell center to network boundary) profile of the continuum intensity contrast associated with supergranular flows using data from the Precision Solar Photometric Telescope (PSPT) at the Mauna Loa Solar Observatory (MLSO). After removing the contribution of the network flux elements by the application of masks based on Ca II K intensity and averaging over more than 10^5 supergranular cells, we find a ~ 0.1% decrease in red and blue continuum intensity from the supergranular cell centers outward, corresponding to a ~ 1.0 K decrease in brightness temperature across the cells. The radial intensity profile may be caused either by the thermal signal associated with the supergranular flows or a variation in the packing density of unresolved magnetic flux elements. These are not unambiguously distinguished by the observations, and we raise the possibility that the network magnetic fields play an active role in supergranular scale selection by enhancing the radiative cooling of the deep photosphere at the cell boundaries.Comment: Accepted to Ap

Radiative emission of solar features in Ca II K

We investigated the radiative emission of different types of solar features in the spectral range of the Ca II K line. We analyzed full-disk 2k x 2k observations from the PSPT Precision Solar Photometric Telescope. The data were obtained by using three narrow-band interference filters that sample the Ca II K line with different pass bands. Two filters are centered in the line core, the other in the red wing of the line. We measured the intensity and contrast of various solar features, specifically quiet Sun (inter-network), network, enhanced network, plage, and bright plage (facula) regions. Moreover, we compared the results obtained with those derived from the numerical synthesis performed for the three PSPT filters with a widely used radiative code on a set of reference semi-empirical atmosphere models.Comment: In Proceedings of the 25th NSO Workshop: Chromospheric Structure and Dynamic

Estimation of soil and vegetation temperatures with multiangular thermal infrared observations: IMGRASS, HEIFE, and SGP 1997 experiments

The potential of directional observations in the thermal infrared region for land surface studies is a largely uncharted area of research. The availability of the dual-view Along Track Scanning Radiometer (ATSR) observations led to explore new opportunities in this direction. In the context of studies on heat transfer at heterogeneous land surfaces, multiangular thermal infrared (TIR) observations offer the opportunity of overcoming fundamental difficulties in modeling sparse canopies. Three case studies were performed on the estimation of the component temperatures of foliage and soil. The first one included the use of multi-temporal field measurements at view angles of 0°, 23° and 52°. The second and third one were done with directional ATSR observations at view angles of 0° and 53° only. The first one was a contribution to the Inner-Mongolia Grassland Atmosphere Surface Study (IMGRASS) experiment in China, the second to the Hei He International Field Experiment (HEIFE) in China and the third one to the Southern Great Plains 1997 (SGP 1997) experiment in Oklahoma, United States. The IMGRASS experiment provided useful insights on the applicability of a simple linear mixture model to the analysis of observed radiance. The HEIFE case study was focused on the large oasis of Zhang-Ye and led to useful estimates of soil and vegetation temperatures. The SGP 1997 contributed a better understanding of the impact of spatial heterogeneity on the accuracy of retrieved foliage and soil temperatures. Limitations in the approach due to varying radiative and boundary layer forcing and to the difference in spatial resolution between the forward and the nadir view are evaluated through a combination of modeling studies and analysis of field data

Understanding the Role of Small-Scale Flux in Solar Spectral Irradiance Variation

Global solar spectral irradiance variations depend on changes inmagnetic flux concentrations at the smallest scales. Modeling has focused on the contributions of magnetic structures in full disk images as those contributions have strong center-to-limb dependencies, but these dependencies have never been determined radiometrically; only the photometric intensity relative to some reference ’quiet-sun’1, themagnetic structure contrast, is measurable with ground based imagery. This is problematic because unre- solved inhomogeneities influence not only the full-disk structure intensities themselves, but also the quiet-sun background against which their contrast is measured. We thus argue that, to understand the physical causes underlying solar spectral irradiance varia- tions, two fundamental questionsmust be addressed: What is the real Iλ(µ) as a function of B in full-disk images? This can only be answered by imaging the Sun radiometrically from space, and we propose a Radiometric Solar Imager design. What governs spectral irradiance changes at sub arc-second scales? This can be addressed by a combination of high resolution ground based imaging (ATST-VBI) and three dimensional radiative magnetohydrodynamic modeling, and we propose a synoptic approach. Finally, a way to account for the variance introduced by unresolved substructure in spectral irradiance modeling must be devised. This is critical, as imaging and modeling at the highest resolutions but over the full solar disk will likely remain unattainable for some time

Dynamic Evolution of Toll-Like Receptor Multigene Families in Echinoderms

The genome sequence of the purple sea urchin, Strongylocentrotus purpuratus, a large and long-lived invertebrate, provides a new perspective on animal immunity. Analysis of this genome uncovered a highly complex immune system in which the gene families that encode homologs of the pattern recognition receptors that form the core of vertebrate innate immunity are encoded in large multigene families. The sea urchin genome contains 253 Toll-like receptor (TLR) sequences, more than 200 Nod-like receptors and 1095 scavenger receptor cysteine-rich domains, a 10-fold expansion relative to vertebrates. Given their stereotypic protein structure and simple intron-exon architecture, the TLRs are the most tractable of these families for more detailed analysis. A role for these receptors in immune defense is suggested by their similarity to TLRs in other organisms, sequence diversity, and expression in immunologically active tissues, including phagocytes. The complexity of the sea urchin TLR multigene families is largely derived from expansions independent of those in vertebrates and protostomes, although a small family of TLRs with structure similar to that of Drosophila Toll can be traced to an ancient eumetazoan ancestor. Several other echinoderm sequences are now available, including Lytechinus variegatus, as well as partial sequences from two other sea urchin species. Here, we present an analysis of the invertebrate deuterostome TLRs with emphasis on the echinoderms. Representatives of most of the S. purpuratus TLR subfamilies and homologs of the mccTLR sequences are found in L. variegatus, although the L. variegatus TLR gene family is notably smaller (68 TLR sequences). The phylogeny of these genes within sea urchins highlights lineage-specific expansions at higher resolution than is evident at the phylum level. These analyses identify quickly evolving TLR subfamilies that are likely to have novel immune recognition functions and other, more stable, subfamilies that may function more similarly to those of vertebrates