The Inconvenient Truth About Coronal Dimmings

We investigate the occurrence of a CME-driven coronal dimming using unique high resolution spectral images of the corona from the Hinode spacecraft. Over the course of the dimming event we observe the dynamic increase of non-thermal line broadening in the 195.12Angstrom emission line of Fe XII as the corona opens. As the corona begins to close, refill and brighten, we see a reduction of the non-thermal broadening towards the pre-eruption level. We propose that the dynamic evolution of non-thermal broadening is the result of the growth of Alfven wave amplitudes in the magnetically open rarefied dimming region, compared to the dense closed corona prior to the CME. We suggest, based on this proposition, that, as open magnetic regions, coronal dimmings must act just as coronal holes and be sources of the fast solar wind, but only temporarily. Further, we propose that such a rapid transition in the thermodynamics of the corona to a solar wind state may have an impulsive effect on the CME that initiates the observed dimming. This last point, if correct, poses a significant physical challenge to the sophistication of CME modeling and capturing the essence of the source region thermodynamics necessary to correctly ascertain CME propagation speeds, etc.Comment: 4 pages, 3 figures, submitted to ApJ - rerouted to ApJ

Observing Evolution in the Supergranular Length Scale During Periods of Low Solar Activity

We present the initial results of an observational study into the variation of the dominant length-scale of quiet solar emission: supergranulation. This length-scale reflects the radiative energy in the plasma of the upper solar chromosphere and transition region at the magnetic network boundaries forming as a result of the relentless interaction of magnetic fields and convective motions of the Sun's interior. We demonstrate that a net difference of ~0.5Mm in the supergranular emission length-scale occurs when comparing observations cycle 22/23 and cycle 23/24 minima. This variation in scale is reproduced in the datasets of multiple space- and ground-based instruments and using different diagnostic measures. By means of extension, we consider the variation of the supergranular length-scale over multiple solar minima by analyzing a subset of the Mt Wilson Solar Observatory (MWO) Ca II K image record. The observations and analysis presented provide a tantalizing look at solar activity in the absence of large-scale flux emergence, offering insight into times of "extreme" solar minimum and general behavior such as the phasing and cross-dependence of different components of the spectral irradiance. Given that the modulation of the supergranular scale imprints itself in variations of the Sun's spectral irradiance, as well as in the mass and energy transport into the entire outer atmosphere, this preliminary investigation is an important step in understanding the impact of the quiet sun on the heliospheric system.Comment: 6 pages, 5 figures - ApJL. We thank Frank Eparvier, Tom Woods, Stan Solomon, Anna Malanushenko, and Rachel Hauser for useful discussions and help with the text, SOHO, STEREO, and the Canadian Space Agency for making their data publicly availabl

The quaternionic KP hierarchy and conformally immersed 2-tori in the 4-sphere

The quaternionic KP hierarchy is the integrable hierarchy of p.d.e obtained by replacing the complex numbers with the quaternions, mutatis mutandis, in the standard construction of the KP hierarchy equations and solutions; it is equivalent to what is often called the Davey-Stewartson II hierarchy. This article studies its relationship with the theory of quaternionic holomorphic 2-tori in HP^1 (which are equivalent to conformally immersed 2-tori in S^4). After describing how the Sato-Segal-Wilson construction of KP solutions (particularly solutions of finite type) carries over to this quaternionic setting, we compare three different notions of "spectral curve": the QKP spectral curve, which arises from an algebra of commuting differential operators; the (unnormalised) Floquet multiplier spectral curve for the related Dirac operator; and the curve parameterising Darboux transforms of a conformal 2-torus in S^4 (in the sense of Bohle, Leschke, Pedit and Pinkall). The latter two are shown to be images of the QKP spectral curve, which need not be smooth. Moreover, it is a singularisation of this QKP spectral curve, rather than the normalised Floquet multiplier curve, which determines the classification of conformally immersed 2-tori of finite spectral genus.Comment: 35 pages. Edited heavily from the original version, mainly to shorten, but also to make minor corrections. To appear in: Tokyo Mathematical Journa

The effect of environmental stressors on the development and behaviour of larval Oryzias latipes

Elevated water temperature and dissolved carbon dioxide (CO2) are two environmental stressors that freshwater organisms face in the Anthropocene. Larval fishes are particularly susceptible to elevation in water parameters, as they are often confined to rearing habitats where temperature and CO2 are nearing species-specific maxima. In this study, 240 freshwater Japanese medaka (Oryzias latipes) eggs were exposed to either control conditions (27˚C, ~ 500 μatm pCO2), elevated water temperature (36˚C), elevated CO2 (~1500 μatm pCO2) or both elevated temperature and CO2 (36˚C, ~1500 μatm pCO2). Exposures were applied either during the early, middle or late developmental stages and the morphological and behavioural data was collected ten days post-hatch. I predicted that elevated temperature and CO2 would decrease hatching success, and produce abnormalities in the swim bladder, spine or heart. In addition, I predicted that fish exposed to the stressors would show a change in swimming behaviour. Of the behavioural parameters observed, a significant difference was found in the distance travelled among the larval fish exposed to the treatments. There was no significant change between treatments or time intervals for hatching success, length or morphology. As rising CO2 and warming are likely to have a consequential impact on freshwater species, further research dedicated to understanding the ramification of climate-induced stressors is imperative.Honours Thesis Course, Department of Biolog

Perspective on the economic evaluation of deep brain stimulation

Parkinson’s disease (PD) is an example of a disease area experiencing increasing use of deep brain stimulation (DBS) to treat symptoms. PD is a major cause of morbidity and has a substantial economic impact on the patients, their caregivers, the health service, and broader social and community services. The PDSURG Collaborators Group reported that DBS surgery for patients with advanced PD improves motor function and quality of life that medical therapy alone at 1 year but there are surgery related side effects in a minority (Williams et al., 2010). The aim of this paper however is to build upon the knowledge generated from evaluating DBS in PD and to provide a detailed perspective on the economic evaluation of DBS more generally with a view to providing a framework for informative design of DBS economic evaluations. This perspective will outline the key categories of resource use pertinent to DBS beyond the surgical scenario and into the broader aspects of follow-up care, adverse events, repeat procedures, social and community care, patient and carer costs, and will explore the importance of handling capital costs of DBS equipment appropriately as well as including costs occurring in the future. In addition, this perspective article will outline the importance of capturing broader aspects of “outcome” or benefits as compared to those traditional clinical measures used. The key message is the importance of employing a broad “perspective” on the measurement and valuation of costs and benefits as well as the importance of adopting the appropriate time horizon for evaluating the costs and benefits of DBS. In order to do this effectively it may be that alternative methods of economic evaluation in health care to the commonly used cost-effectiveness analysis may have to be used, such as cost-benefit analysis (McIntosh et al., 2010)

The demand for post-compulsory education in four European countries

This study seeks to explain changes in the proportion of 16 year olds, 17 year olds and 18 year olds who decide to participate in post-compulsory education. Four countries are considered; Germany, the Netherlands, Sweden and England, over as much of the period from 1960 to the present day as data will allow. An initial inspection of the data reveals non-stationarity in virtually all of the series under consideration, so that a cointegration framework is appropriate. The analysis therefore proceeds using the two-stage procedure proposed by Engle and Granger. The results suggest that the key variable that explains the growth in post-compulsory education participation is the increase in prior academic attainment before the end of compulsory schooling. This is the case particularly for females, males being also influenced by the returns available to offering a higher level of education, and the level of real income available to ''spend'' on education. The level of youth unemployment seems to play only a small part in the decision as to whether to remain in education

The Spectroscopic Footprint of the Fast Solar Wind

We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the photosphere, inner heliosphere and the mapping of the solar wind source region. We focus the bulk of our analysis on interpreting the thermal and spatial dependence of the non-thermal line widths in the ECH as measured by SOHO/SUMER by placing the measurements in context with recent studies of ubiquitous Alfven waves in the solar atmosphere and line profile asymmetries (indicative of episodic heating and mass loading of the coronal plasma) that originate in the strong, unipolar magnetic flux concentrations that comprise the supergranular network. The results presented in this paper are consistent with a picture where a significant portion of the energy responsible for the transport of heated mass into the fast solar wind is provided by episodically occurring small-scale events (likely driven by magnetic reconnection) in the upper chromosphere and transition region of the strong magnetic flux regions that comprise the supergranular network.Comment: 25 pages, accepted to appear in the Astrophysical Journal. Supporting movies can be found in http://download.hao.ucar.edu/pub/mscott/papers/ECH