Physical Properties of White-Light Sources in the 2011 Feb 15 Solar Flare

White light flares (WLFs) are observational rarities, making them understudied events. However, optical emission is a significant contribution to flare energy budgets and the emission mechanisms responsible could have important implications for flare models. Using Hinode SOT optical continuum data taken in broadband red, green and blue filters, we investigate white-light emission from the X2.2 flare SOL2011-02-15T01:56:00. We develop a technique to robustly identify enhanced flare pixels and, using a knowledge of the RGB filter transmissions, determined the source color temperature and effective temperature. We investigated two idealized models of WL emission - an optically thick photospheric source, and an optically thin chromospheric slab. Under the optically thick assumption, the color temperature and effective temperature of flare sources in sunspot umbra and penumbra were determined as a function of time and position. Values in the range of 5000-6000K were found, corresponding to a blackbody temperature increase of a few hundred kelvin. The power emitted in the optical was estimated at $\sim 10^{26}$ergs s$^{-1}$. In some of the white-light sources the color and blackbody temperatures are the same within uncertainties, consistent with a blackbody emitter. In other regions this is not the case, suggesting that some other continuum emission process is contributing. An optically thin slab model producing hydrogen recombination radiation is also discussed as a potential source of WL emission; it requires temperatures in the range 5,500 - 25,000K, and total energies of $\sim 10^{27}$ergs s$^{-1}$.Comment: Accepted for publication in the Astrophysical Journal, 15 pages, 15 figure

Determining Energy Balance in the Flaring Chromosphere from Oxygen V Line Ratios

The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. We use an O V density diagnostic formed of the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a constraint on the properties of the heated transition region. Hinode EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionization and optically thin radiation for the O V lines were found to be acceptable. Properties of the electron distribution, for one event, were deduced from earlier RHESSI hard X-ray observations and used to calculate the plasma heating rate, delivered by an electron beam adopting collisional thick-target assumptions, for 2 model atmospheres. Electron number densities of at least log n = 12.3 cm-3 were measured during the flare impulsive phase, far higher than previously expected. For one footpoint, the radiative loss rate for this plasma was found to exceed that which can be delivered by an electron beam implied by the RHESSI data. However, when assuming a completely ionised target atmosphere the heating rate exceeded the losses. A chromospheric thickness of 70-700 km was found to be required to balance a conductive input to the O V-emitting region with radiative losses. The analysis shows that for heating by collisional electrons, it is difficult, or impossible to raise the temperature of the chromosphere to explain the observed densities without assuming a completely ionised atmosphere.Comment: Accepted to A&A 14th September 201

A New Perspective Concerning Place, Reconciliation, and Judgment via a Consideration of the Nexus between Christianity and Indigenous Spirituality

The paper first offers a brief overview of some key concepts of Native Title, inclusive of key dates and events significant to the current native title issues in Australia. It then proffers a new perspective concerning three key issues relevant to the nexus between Christianity and Indigenous spiritualities, namely (a) the importance of place, (b) reconcilitation, and (c) the judgment

Observations and Modelling of Helium Lines in Solar Flares

We explore the response of the He II 304 Å and He I 584 Å line intensities to electron beam heating in solar flares using radiative hydrodynamic simulations. Comparing different electron beams parameters, we found that the intensities of both He lines are very sensitive to the energy flux deposited in the chromosphere, or more specifically to the heating rate, with He II 304 {\AA} being more sensitive to the heating than He I 584 {\AA}. Therefore, the He line ratio increases for larger heating rates in the chromosphere. A similar trend is found in observations, using SDO/EVE He irradiance ratios and estimates of the electron beam energy rate obtained from hard X-ray data. From the simulations, we also found that spectral index of the electrons can affect the He ratio but a similar effect was not found in the observations

Impulsive Heating of Solar Flare Ribbons Above 10 MK

The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from accelerated electrons colliding in the dense chromospheric plasma. We present evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class event using data from Atmospheric Imaging Assembly (AIA) on board of Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and differential emission measure of the flaring regions and investigate the evolution of the plasma in the flaring ribbons. The ribbons were visible at all SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 \AA\ filters, sensitive to temperatures of 8 MK and 12 MK. Time evolution of the emission measure of the plasma above 10 MK at the ribbons has a peak near the HXR peak time. The presence of hot plasma in the lower atmosphere is further confirmed by RHESSI imaging spectroscopy analysis, which shows resolved sources at 11-13 MK associated with at least one ribbon. We found that collisional beam heating can only marginally explain the necessary power to heat the 10 MK plasma at the ribbons.Comment: 21 pages, 15 figure

The use of a second excipient to alter the characteristics of PVP-drug solid dispersions

Many drugs are poorly water soluble and this can limit bioavailability. One way of increasing the dissolution rate and apparent saturation solubility of a poorly water soluble drug is to prepare a solid dispersion. The ideal solid dispersion is one in which the drug and excipient (typically a polymer) are molecularly dispersed. This dispersion may be unstable. Phase separation and recrystallisation of the drug may occur. The aims of this work were to investigate how the use of a second excipient affects the dissolution of a stable amorphous PVP-drug dispersion, how the use of a second excipient affects the amorphous stability of unstable PVP-dispersions and whether near infrared spectroscopy (NIRS) could be used as a technique to detect crystallisation. Indomethacin was spray-dried with PVP and a variety of second excipients. Characterisation was performed using differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA) and dissolution studies at pH 1.2, 6.5 and 7.0. At pH 6.5, indomethacin dissolved from all the solid dispersions bar one containing Eudragit S. This dispersion proved to be soluble above pH 7.0. When the dispersion was prepared by dissolving the components of the dispersion in a different order prior to spray drying the dispersion was then found to dissolve suggesting that differences in non-covalent bonding were occurring. Griseofulvin, flavanone and clotrimazole were all spray-dried with PVP and a variety of second excipients. Characterisation was performed using DSC, XRPD and TGA. The addition of poly(2-hydroxypropylmethacrylate) (PHPMA) was found to improve the amorphous stability of griseofulvin dispersions when stored at 0% and 30% relative humidity (RH) though this was later found to be dependent on the order in which components were dissolved. PHPMA was also found to improve the amorphous stability of flavanone when stored at 0% RH. Sucrose was found to improve the amorphous stability of clotrimazole when stored at room temperature, 0% RH. When dispersions containing lower concentrations of clotrimazole were prepared this benefit was lost although the addition of poly(acrylic acid) to the dispersion did seem to improve the amorphous stability. NIRS investigations of the amorphous stability of griseofulvin dispersions showed that the technique was less sensitive than XRPD, though it may provide some information about the mechanism of stabilisation

IRIS Observations of the Mg II h & k Lines During a Solar Flare

The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg II h & k resonance lines. We present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare (SOL2014-02-13T01:40). Very intense, spatially localised energy input at the outer edge of the ribbon is observed, resulting in redshifts equivalent to velocities of ~15-26km/s, line broadenings, and a blue asymmetry in the most intense sources. The characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles, indicating that the source function increases with height during the flare. Despite the absence of the central reversal feature, the k/h line ratio indicates that the lines remain optically thick during the flare. Subordinate lines in the Mg II passband are observed to be in emission in flaring sources, brightening and cooling with similar timescales to the resonance lines. This work represents a first analysis of potential diagnostic information of the flaring atmosphere using these lines, and provides observations to which synthetic spectra from advanced radiative transfer codes can be compared.Comment: 12 pages, 14 figures, Accepted for publication in Astronomy and Astrophysic

Designing a knowledge distribution simulator

To make good decisions, we need to be suitably informed. \u27Good\u27 and \u27Suitably\u27 in this case depend on the informational needs of the decision and the mechanisms of getting the information to the decision maker in time. The trade-offs in qualities, quantities, timeliness, impacts on other activities, and so on are infamously wickedly complex, and usually buried in a clutter of special circumstances, personality characteristics, environments unsuitable for study, and so on. Decision-making systems can be explored using case studies and exercises, but these are limited by the expense and time of using real people. A virtual simulator for large scale networks of communities can provide systems to examine that are not otherwise possible, while bearing in mind that simulators only partially reflect real systems. This paper describes a design for such a simulator framework that can be implemented on an ordinary desktop computer. We intend to use it to exercise and explore various ‘knowledge distribution strategies’ in order to understand and suggest information communication mechanisms for investigation in the real world, without expecting it to be complete enough to be prescriptive. We focus on military collaborations as suitably \u27eXtreme\u27 environments to exercise these communication mechanisms. Topics for further investigation include isolation, turnover and resilience

A study of the design and analysis of feed-forward neural networks

This thesis shows that a design and analysis system for feed forward neural networks is desirable, and that the currently available techniques do not work. Methods have been presented that solve the problem of analysis, showing that analysis is possible and desirable for classification networks. The biggest limitation is the size of the network and that the analysis tools are only applicable to properly designed classification systems. A method of reducing the size of classification networks is presented along with a design methodology for non classification systems