Hard X-ray footpoint sizes and positions as diagnostics of flare accelerated energetic electrons in the low solar atmosphere

The hard X-ray (HXR) emission in solar flares comes almost exclusively from a very small part of the flaring region, the footpoints of magnetic loops. Using RHESSI observations of solar flare footpoints, we determine the radial positions and sizes of footpoints as a function of energy in six near-limb events to investigate the transport of flare accelerated electrons and the properties of the chromosphere. HXR visibility forward fitting allows to find the positions/heights and the sizes of HXR footpoints along and perpendicular to the magnetic field of the flaring loop at different energies in the HXR range. We show that in half of the analyzed events, a clear trend of decreasing height of the sources with energy is found. Assuming collisional thick-target transport, HXR sources are located between 600 and 1200 km above the photosphere for photon energies between 120 and 25 keV respectively. In the other events, the position as a function of energy is constant within the uncertainties. The vertical sizes (along the path of electron propagation) range from 1.3 to 8 arcseconds which is up to a factor 4 larger than predicted by the thick-target model even in events where the positions/heights of HXR sources are consistent with the collisional thick-target model. Magnetic mirroring, collisional pitch angle scattering and X-ray albedo are discussed as potential explanations of the findings.Comment: 10 pages, 8 figures, accepted for publication in Ap

Student Presentations

Four students presented their semester-long research findings pertaining to both the art and science of fashion. Hannah Doster and Marissa Cardullo investigated the influences of art on fashion. Hannah and Marissa researched surrealism in the 1930s and art movements from the 1960s, respectively. Alaina Cardillo and Allyson Conway researched the science behind fashion with topics including UV protection in apparel and 3D printing

The sub-arcsecond hard X-ray structure of loop footpoints in a solar flare

The newly developed X-ray visibility forward fitting technique is applied to Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data of a limb flare to investigate the energy and height dependence on sizes, shapes, and position of hard X-ray chromospheric footpoint sources. This provides information about the electron transport and chromospheric density structure. The spatial distribution of two footpoint X-ray sources is analyzed using PIXON, Maximum Entropy Method, CLEAN and visibility forward fit algorithms at nonthermal energies from $\sim 20$ to $\sim 200$ keV. We report, for the first time, the vertical extents and widths of hard X-ray chromospheric sources measured as a function of energy for a limb event. Our observations suggest that both the vertical and horizontal sizes of footpoints are decreasing with energy. Higher energy emission originates progressively deeper in the chromosphere consistent with downward flare accelerated streaming electrons. The ellipticity of the footpoints grows with energy from $\sim 0.5$ at $\sim 20$ keV to $\sim 0.9$ at $\sim 150$ keV. The positions of X-ray emission are in agreement with an exponential density profile of scale height $\sim 150$~km. The characteristic size of the hard X-ray footpoint source along the limb is decreasing with energy suggesting a converging magnetic field in the footpoint. The vertical sizes of X-ray sources are inconsistent with simple collisional transport in a single density scale height but can be explained using a multi-threaded density structure in the chromosphere.Comment: 7 pages, 7 figures, submitted to Ap

From advocacy to action: projecting the health impacts of climate change

Mitigating climate change by reducing greenhouse gas emissions has many measurable co-benefits for public health and remains a priority (Haines et al., 2009). However, recognition that climate change is already underway has led to an increasing focus on adaptation. Studies projecting the impacts of future climate change on health date back to the late 1980s and their number has grown substantially in recent years. Climate change impact assessments generally use the output of global climate models (GCMs). Here we profile, and suggest means for addressing, challenges associated with the use of GCM projections and impact studies to inform adaptation

Expression and function of ATP-dependent potassium channels in zebrafish islet β-cells

ATP-sensitive potassium channels (K(ATP) channels) are critical nutrient sensors in many mammalian tissues. In the pancreas, K(ATP) channels are essential for coupling glucose metabolism to insulin secretion. While orthologous genes for many components of metabolism–secretion coupling in mammals are present in lower vertebrates, their expression, functionality and ultimate impact on body glucose homeostasis are unclear. In this paper, we demonstrate that zebrafish islet β-cells express functional K(ATP) channels of similar subunit composition, structure and metabolic sensitivity to their mammalian counterparts. We further show that pharmacological activation of native zebrafish K(ATP) using diazoxide, a specific K(ATP) channel opener, is sufficient to disturb glucose tolerance in adult zebrafish. That β-cell K(ATP) channel expression and function are conserved between zebrafish and mammals illustrates the evolutionary conservation of islet metabolic sensing from fish to humans, and lends relevance to the use of zebrafish to model islet glucose sensing and diseases of membrane excitability such as neonatal diabetes

The effects of early years' childcare on child emotional and behavioural difficulties in lone and co-parent family situations

With targeted childcare initiatives and welfare-to-work programmes policy-makers have sought to address employment activation of lone mothers and negative outcomes for children in lone parent households. The present study examines non-parental childcare use and maternal employment among children living in lone and co-parent family situations at ages three and four and emotional and behavioural difficulties at ages four and five. The results demonstrate that negative outcomes associated with lone motherhood are explained largely by mother's age, education, material circumstances and area deprivation; and that maternal employment does not relieve lone mothers’ disadvantages in a way that alleviates the risks of difficulties to their children. However, in any family constellation, mainly group-based formal pre-school childcare does have a positive impact on child difficulties compared to drawing on informal childcare arrangements as main provider. In addition, and specifically for the difficulties of children in lone mother family situations, any non-parental childcare – formal or informal − for at least twenty-five hours per week is beneficial. Study findings support policy agendas which tackle families’ material hardship beyond promoting mothers’ employment, and through investment in formal childcare provision, and also through arrangements allowing lone mothers to divide their weekly load of childcare with another main provider

Legal Deserts: A Multi-State Perspective on Rural Access to Justice

Rural America faces an increasingly dire access-to-justice crisis, which serves to exacerbate the already disproportionate share of social problems afflicting rural areas. One critical aspect of the crisis is the dearth of information and research regarding the extent of the problem and its impacts. This Article begins to fill that gap by providing surveys of rural access to justice in six geographically, demographically, and economically varied states: California, Georgia, Maine, Minnesota, South Dakota, and Wisconsin. In addition to providing insights about the distinct rural challenges confronting each of these states, the legal resources available, and existing policy responses, the Article explores common themes that emerge through this multi-state lens, with particular attention to the rural attorney shortage, thus framing a richer, broader discussion of rural access to justice. Written for a special issue on Revitalizing Rural, this Article ultimately proposes a two-step approach to alleviate rural justice deficits. First, although the information presented here provides a solid foundation, a critical need remains for ongoing, careful, and thoughtful study of the legal needs and lack of legal resources in rural areas. Second, the unique institutional, structural, and demographic characteristics of rural areas will require tailored, innovative, and data-driven solutions to match appropriate legal services with needs. We advocate a re-thinking of the roles of many justice system stakeholders, including the critical steps that legal educators can and should take to help close the rural-urban justice gap. Our hope is that this Article will inform and expand access-to-justice conversations so that they more intentionally address the legal needs of the vast rural reaches of our nation, thus furthering the ultimate goal of realizing access to justice for all Americans

Multiwavelength radio observations of the compact starburst in Arp 220

We report the first detection at multiple radio wavelengths (13, 6, and 3.6 cm) of 18 compact sources within both nuclei of the Ultra Luminous Infra-Red Galaxy (ULIRG) Arp 220. In just over half of the sources we find that the observed spectra are consistent with the standard model of powerful Type IIn supernovae interacting with their pre-explosion stellar wind. The rate of appearance of new radio sources ascribed to these supernova events suggests that a large fraction of core-collapse supernovae in Arp 220 are highly luminous, possibly implying a radically different stellar initial mass function (IMF) or stellar evolution compared to galactic disks. A second group of sources, consisting of the brightest and longest monitored sources at 18 cm, do not easily fit the radio supernova model. We propose that these are young supernova remnants that have just begun interacting with their surrounding dense ISM

Perceived Neighborhood Environmental Attributes Associated with Walking and Cycling for Transport among Adult Residents of 17 Cities in 12 Countries: The IPEN Study

Introduction Prevalence of walking and cycling for transport is low and varies greatly across countries. Few studies have examined neighborhood perceptions related to walking and cycling for transport in different countries. Therefore, it is challenging to prioritize appropriate built-environment interventions. Objectives The aim of this study was to examine the strength and shape of the relationship between adults’ neighborhood perceptions and walking and cycling for transport across diverse environments. Methods As part of the International Physical activity and Environment Network (IPEN) adult project, self-reported data were taken from 13,745 adults (18–65 years) living in physically and socially diverse neighborhoods in 17 cities across 12 countries. Neighborhood perceptions were measured using the Neighborhood Environment Walkability Scale, and walking and cycling for transport were measured using the International Physical Activity Questionnaire–Long Form. Generalized additive mixed models were used to model walking or cycling for transport during the last seven days with neighborhood perceptions. Interactions by city were explored. Results Walking-for-transport outcomes were significantly associated with perceived residential density, land use mix–access, street connectivity, aesthetics, and safety. Any cycling for transport was significantly related to perceived land use mix–access, street connectivity, infrastructure, aesthetics, safety, and perceived distance to destinations. Between-city differences existed for some attributes in relation to walking or cycling for transport. Conclusions Many perceived environmental attributes supported both cycling and walking; however, highly walkable environments may not support cycling for transport. People appear to walk for transport despite safety concerns. These findings can guide the implementation of global health strategies