Probing sunspots with two-skip time-distance helioseismology

Previous helioseismology of sunspots has been sensitive to both the structural and magnetic aspects of sunspot structure. We aim to develop a technique that is insensitive to the magnetic component so the two aspects can be more readily separated. We study waves reflected almost vertically from the underside of a sunspot. Time-distance helioseismology was used to measure travel times for the waves. Ray theory and a detailed sunspot model were used to calculate travel times for comparison. It is shown that these large distance waves are insensitive to the magnetic field in the sunspot. The largest travel time differences for any solar phenomena are observed. With sufficient modeling effort, these should lead to better understanding of sunspot structure

The five-minute oscillations: What's left to be done

Current observational methods for studying these oscillations at large horizontal wavenumbers are discussed in detail and several two dimensional power spectra obtained with a CID camera on the main spectrograph of the McMath telescope at Kitt Peak National Observatory are described. The best-resolved observations of the p-mode obtained at chromospheric elevations are also presented. Recent progress in studies of the p-modes at low wavenumbers with full-disk velocity detection schemes is summarized. These full-disk observations of radial and low-degree non-radial modes were shown to place severe constraints on the theoretical calculation of solar interior structure. Progress in making fully-consistent solar models which fit both the high- and low-wave number observations is described. Finally, the observational and theoretical improvements that are necessary for further progress in solar seismology are summarized

Predictive Validation of a Computer Programmer Selection Test

Subjects were 32 computer programmers employed in a large computerized tax-processing company in the Southwest. Ratings of each programmer's job performance by his/her immediate supervisor and scores on the Aptitude Test for Programmer Personnel (ATPP) were obtained. Relationships between test scores and criteria were examined to identify significant (p .05) the rated performance of the programmers

Balltracking: an highly efficient method for tracking flow fields

We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tested against synthesised granulation with known flow fields and compared to the results produced by Local Correlation tracking (LCT). The results from this new method have similar accuracy to those produced by LCT. We also investigate the maximum spatial and temporal resolution of the velocity field that it is possible to extract, based on the statistical properties of the granulation data. We conclude that both methods produce results that are close to the maximum resolution possible from granulation data. The code runs very significantly faster than our similarly optimised LCT code, making real time applications on large data sets possible. The tracking method is not limited to photospheric flows, and will also work on any velocity field where there are visible moving features of known scale length

The mean magnetic field of the sun: Observations at Stanford

A solar telescope was built at Stanford University to study the organization and evolution of large-scale solar magnetic fields and velocities. The observations are made using a Babcock-type magnetograph which is connected to a 22.9 m vertical Littrow spectrograph. Sun-as-a-star integrated light measurements of the mean solar magnetic field were made daily since May 1975. The typical mean field magnitude is about 0.15 gauss with typical measurement error less than 0.05 gauss. The mean field polarity pattern is essentially identical to the interplanetary magnetic field sector structure (seen near the earth with a 4 day lag). The differences in the observed structures can be understood in terms of a warped current sheet model

Examining the Effects on Salivary Cortisol Levels of Shelter Volunteers Interacting with Familiar Dogs

Heightened cortisol levels are a typical physiological response to stress. The many responsibilities of animal shelter workers can lead to increased stress levels and negative effects on their job satisfaction and overall wellness. As a result, workers are subject to burnout and compassion fatigue. While working in shelter environments may be stressful, interactions with dogs have been found to help people manage their mental as well as physical health. The purpose of this study was to evaluate the physiologic stress response of shelter volunteers following interactions with dogs that they work with. Saliva samples were taken from seventeen participating shelter volunteers before and after interacting with a chosen familiar shelter dog from Willamette Humane Society through a 12 minute testing session consisting of a Secure Base Test and a Paired Attachment Test. Lexington Attachment to Pets Scale survey scores were also analyzed for the purpose of this study. No significant correlations were found with respect to cortisol levels and results of the behavioral tests or survey scores. In conclusion, the shelter volunteers of Willamette Humane Society were found to be stable in this environment and do not necessarily have a change in stress levels after interacting with a familiar dog

Widespread late Cenozoic increase in erosion rates across the interior of eastern Tibet constrained by detrital low-temperature thermochronometry

New detrital low-temperature thermochronometry provides estimates of long-term erosion rates and the timing of initiation of river incision from across the interior of the Tibetan Plateau. We use the erosion history of this region to evaluate proposed models of orogenic development as well as regional climatic events. Erosion histories of the externally drained portion of the east-central Tibetan Plateau are recorded in modern river sands from major rivers across a transect that spans >750 km and covers a region with no published thermochronometric ages. Individual grains from eight catchments were analyzed for apatite (U-Th)/He and fission track thermochronometry. A wide distribution in ages that, in most cases, spans the entire Cenozoic and Late Mesozoic eras requires a long period of slow or no erosion with a relative increase in erosion rate toward the present. We apply a recently developed methodology for inversion of detrital thermochronometric data for three specified erosion scenarios: constant erosion rate, two-stage erosion history, and three-stage erosion history. Modeling results suggest that rates increase by at least an order of magnitude between 11 and 4 Ma following a period of slow erosion across the studied catchments. Synchroneity in accelerated erosion across the whole of the Tibetan Plateau rather than a spatial or temporal progression challenges the widely held notion that the plateau evolved as a steep, northward-propagating topographic front, or that south to north precipitation gradients exert a primary control on erosion rates. Instead, we suggest that accelerated river incision late in the orogen's history relates to regional-scale uplift that occurred in concert with eastern expansion of the plateau

Time-distance analysis of the emerging active region NOAA 10790

We investigate the emergence of Active Region NOAA 10790 by means of time – distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic-flux and thus obtain a provisional estimate of the speed of emergence of around 1 km s−1

Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory