Acoustic wave propagation in the solar sub-photosphere with localised magnetic field concentration: effect of magnetic tension

Aims: We analyse numerically the propagation and dispersion of acoustic waves in the solar-like sub-photosphere with localised non-uniform magnetic field concentrations, mimicking sunspots with various representative magnetic field configurations. Methods: Numerical simulations of wave propagation through the solar sub-photosphere with a localised magnetic field concentration are carried out using SAC, which solves the MHD equations for gravitationally stratified plasma. The initial equilibrium density and pressure stratifications are derived from a standard solar model. Acoustic waves are generated by a source located at the height corresponding approximately to the visible surface of the Sun. By means of local helioseismology we analyse the response of vertical velocity at the level corresponding to the visible solar surface to changes induced by magnetic field in the interior. Results: The results of numerical simulations of acoustic wave propagation and dispersion in the solar sub-photosphere with localised magnetic field concentrations of various types are presented. Time-distance diagrams of the vertical velocity perturbation at the level corresponding to the visible solar surface show that the magnetic field perturbs and scatters acoustic waves and absorbs the acoustic power of the wave packet. For the weakly magnetised case, the effect of magnetic field is mainly thermodynamic, since the magnetic field changes the temperature stratification. However, we observe the signature of slow magnetoacoustic mode, propagating downwards, for the strong magnetic field cases

Comparison of H alpha synoptic charts with the large-scale solar magnetic field as observed at Stanford

Two methods of observing the neutral line of the large-scale photospheric magnetic field are compared: (1) neutral line positions inferred from H alpha photographs and (2) observations of the photospheric magnetic field made with low spatial resolution (3 arc min.) and high sensitivity using the Stanford magnetograph. The comparison is found to be very favorable

Mobile Learning

During the Fall of 2003, the East Carolina University Center for Wireless and Mobile Computing and Sprint PCS/Airgate Communications implemented a project to evaluate the potential of 3G smart phone/handheld computers (3GCD’s) for mobile learning. The first environment that was selected for testing this technology involved on-campus freshman Teaching Fellows in the College of Education. In the spring of 2004, the project was expanded to evaluate the use of the devices with twenty-four students taking an online class in Business, Career, and Technical Education. This article will share information on of the use of 3GCD’s with online students.During the Fall of 2003, the East Carolina University Center for Wireless and Mobile Computing and Sprint PCS/Airgate Communications implemented a project to evaluate the potential of 3G smart phone/handheld computers (3GCD’s) for mobile learning. The first environment that was selected for testing this technology involved on-campus freshman Teaching Fellows in the College of Education. In the spring of 2004, the project was expanded to evaluate the use of the devices with twenty-four students taking an online class in Business, Career, and Technical Education. This article will share information on of the use of 3GCD’s with online students

Demographic Data of Patients seen in a Medical Genetics Clinic for Autism Spectrum Disorders (ASD) as part of an ongoing study on “Genetic Variations in ASD”.

Background: Autism spectrum disorder (ASD) is a lifelong developmental disability defined by deficits in social communication and social interaction and restricted, repetitive patterns of behavior, interests, or activities. Over the last few decades, the global prevalence of autism has increased by twentyfold to thirtyfold. In the United States, the prevalence of ASD has increased rapidly with one out of every fifty-nine children (1.7%) diagnosed with the condition. With the increasing prevalence of ASD, the financial cost has been estimated to exceed those of Diabetes and Attention Deficit Hyperactivity Disorder (ADHD) by 2025. Furthermore, ASD has been found to be about 4-5 times more prevalent in males, compared to females, and there has been a noted increase in the prevalence of congenital abnormalities in patients with ASD. Objective: As part of an ongoing multi-year retrospective chart review of the patients seen at the Genetics Clinic for suspected or confirmed cases of ASD, we sought to identify the demographic characteristics of these patients and to see how they compare with documented studies. Methods: The overall study is an ongoing multi-year, retrospective chart review of patients seen at the ETSU Medical Genetics Clinic, with features suggestive of ASD. For this preliminary study, we extracted data from the Electronic health record (Allscripts) for 80 patients (n=80), on the gender, term status at birth (term defined as gestational age at delivery of 37 weeks or more, preterm defined as those delivered at less than 37 weeks), twin status, presence of congenital abnormalities, and the state of residence. We entered all the extracted data into REDCap and carried out a descriptive analysis of the data using the Statistical Package for Social Sciences (SPSS). Results: It was found that of the eighty patients, eighteen (22.5%) were females while sixty-two (77.5%) were males, (male to female ratio of 3.4 to 1). Fifty-nine patients (73.8%) were born at term, eighteen (22.5%) born preterm and three (3.8%) with unknown term status. Seventy-seven patients (96.3%) were twins and three (3.8%) were not. Thirty patients (37.5%) had no congenital abnormalities at birth while fifty patients (62.5%) had at least one congenital abnormality at birth. Sixty-one patients (76.3%) were from Tennessee while nineteen (23.8%) were from Virginia. Conclusions: This preliminary finding revealed an increased proportion of males compared to females, as well as an increased proportion of the population with congenital abnormalities compared to those without such abnormality. These findings agree with documented data from previous studies on ASD. In our future analysis, we would examine the rate of diagnosis of ASD in the clinic, the type of mutation and the genes involved and identify any trend for specific genes, and/or specific mutation

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

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

Allometry of sodium requirements and mineral lick use among herbivorous mammals

Sodium (Na) plays a critical role in the functioning of terrestrial ecosystems. In Na-poor regions, plant consumers may experience Na deficiency and adapt by seeking supplementary Na resources. This can markedly impact animal behavior, space-use, and co-existence, with concomitant impacts on ecosystems. Many studies have noted that Na-seeking behaviors, such as soil consumption from mineral licks, are predominately observed for larger-bodied herbivores. However, the mechanisms that drive interspecific variation in Na deficiency and mineral lick use remain poorly understood. Here, we examine whether allometric scaling of Na requirements can explain variation in mineral lick use by herbivorous and omnivorous mammals. We 1) collated data from published literature to derive an allometric scaling of Na requirements in mammals, 2) compared predicted Na requirements to estimated Na intake of mammal communities in three globally distant sites: the Peruvian Amazon, Kalahari Desert, and Malaysian Borneo and 3) examined the relationship between predicted Na deficiency and mineral lick use utilizing camera-trap and mammal abundance data at each site. We found that minimum daily Na maintenance requirements in mammals scaled allometrically at a higher factor (BM0.91 (CI: 0.80–1.0)) than that of food and water Na intake (BM0.71–0.79), indicating that larger species may be more susceptible to Na limitation. This aligned with a positive association between mineral lick use and body mass (BM), as well as Na deficiency, by species at all sites, and increased artificial salt and mineral lick consumption by larger-bodied mammals in the Kalahari. Our results suggest that larger herbivores may be more sensitive to anthropogenic impacts to Na availability, which may alter their functional roles in ecosystems, particularly in Na-poor regions. Further research is needed to explore the consequences of changing Na availability on animals and ecosystems, as well as advance our understanding of Na physiology in mammals

Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time-Distance Helioseismology

As large--distance rays (say, 10\,-\,$24 ^\circ$) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time-distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant travel time signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center--annulus travel time difference $[\delta t_{\rm{oi}}]$ in the separation range $\Delta=10$\,-\,$24 ^\circ$ is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a constant signal from the vertical flow. Our measurement of this quantity, 5.1 \pm 0.1\secs, is constant over the distance range. This magnitude of signal cannot be caused by the level of upflow at cell centers seen at the photosphere of 10\ms extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of 240\ms at a depth of 2.3\Mm and a peak horizontal flow of 700\ms at a depth of 1.6\Mm.Comment: Solar Physics; 15 pages, 6 figure

Fourier Analysis of Gapped Time Series: Improved Estimates of Solar and Stellar Oscillation Parameters

Quantitative helio- and asteroseismology require very precise measurements of the frequencies, amplitudes, and lifetimes of the global modes of stellar oscillation. It is common knowledge that the precision of these measurements depends on the total length (T), quality, and completeness of the observations. Except in a few simple cases, the effect of gaps in the data on measurement precision is poorly understood, in particular in Fourier space where the convolution of the observable with the observation window introduces correlations between different frequencies. Here we describe and implement a rather general method to retrieve maximum likelihood estimates of the oscillation parameters, taking into account the proper statistics of the observations. Our fitting method applies in complex Fourier space and exploits the phase information. We consider both solar-like stochastic oscillations and long-lived harmonic oscillations, plus random noise. Using numerical simulations, we demonstrate the existence of cases for which our improved fitting method is less biased and has a greater precision than when the frequency correlations are ignored. This is especially true of low signal-to-noise solar-like oscillations. For example, we discuss a case where the precision on the mode frequency estimate is increased by a factor of five, for a duty cycle of 15%. In the case of long-lived sinusoidal oscillations, a proper treatment of the frequency correlations does not provide any significant improvement; nevertheless we confirm that the mode frequency can be measured from gapped data at a much better precision than the 1/T Rayleigh resolution.Comment: Accepted for publication in Solar Physics Topical Issue "Helioseismology, Asteroseismology, and MHD Connections

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