RHESSI and SOHO/CDS Observations of Explosive Chromospheric Evaporation

Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) onboard SOHO. For the first time, co-spatial imaging and spectroscopy have been used to observe explosive evaporation within a hard X-ray emitting region. RHESSI X-ray images and spectra were used to determine the flux of non-thermal electrons accelerated during the impulsive phase of an M2.2 flare. Assuming a thick-target model, the injected electron spectrum was found to have a spectral index of ~7.3, a low energy cut-off of ~20 keV, and a resulting flux of >4x10^10 ergs cm^-2 s^-1. The dynamic response of the atmosphere was determined using CDS spectra, finding a mean upflow velocity of 230+/-38 km s^-1 in Fe XIX (592.23A), and associated downflows of 36+/-16 km s^-1 and 43+/-22 km s^-1 at chromospheric and transition region temperatures, respectively, relative to an averaged quiet-Sun spectra. The errors represent a 1 sigma dispersion. The properties of the accelerated electron spectrum and the corresponding evaporative velocities were found to be consistent with the predictions of theory.Comment: 5 pages, 4 figures, ApJL (In Press

Using variograms to detect and attribute hydrological change

There have been many published studies aiming to identify temporal changes in river flow time series, most of which use monotonic trend tests such as the Mann–Kendall test. Although robust to both the distribution of the data and incomplete records, these tests have important limitations and provide no information as to whether a change in variability mirrors a change in magnitude. This study develops a new method for detecting periods of change in a river flow time series, using temporally shifting variograms (TSVs) based on applying variograms to moving windows in a time series and comparing these to the long-term average variogram, which characterises the temporal dependence structure in the river flow time series. Variogram properties in each moving window can also be related to potential meteorological drivers. The method is applied to 91 UK catchments which were chosen to have minimal anthropogenic influences and good quality data between 1980 and 2012 inclusive. Each of the four variogram parameters (range, sill and two measures of semi-variance) characterise different aspects of the river flow regime, and have a different relationship with the precipitation characteristics. Three variogram parameters (the sill and the two measures of semi-variance) are related to variability (either day-to-day or over the time series) and have the largest correlations with indicators describing the magnitude and variability of precipitation. The fourth (the range) is dependent on the relationship between the river flow on successive days and is most correlated with the length of wet and dry periods. Two prominent periods of change were identified: 1995–2001 and 2004–2012. The first period of change is attributed to an increase in the magnitude of rainfall whilst the second period is attributed to an increase in variability of the rainfall. The study demonstrates that variograms have considerable potential for application in the detection and attribution of temporal variability and change in hydrological systems

An investigation of Fe XV emission lines in solar flare spectra

Previously, large discrepancies have been found between theory and observation for Fe XV emission line ratios in solar flare spectra covering the 224-327 A wavelength range, obtained by the Naval Research Laboratory's S082A instrument on board Skylab. These discrepancies have been attributed to either errors in the adopted atomic data or the presence of additional atomic processes not included in the modelling, such as fluorescence. However our analysis of these plus other S082A flare observations (the latter containing Fe XV transitions between 321-482 A), performed using the most recent Fe XV atomic physics calculations in conjunction with a CHIANTI synthetic flare spectrum, indicate that blending of the lines is primarily responsible for the discrepancies. As a result, most Fe XV lines cannot be employed as electron density diagnostics for solar flares, at least at the spectral resolution of S082A and similar instruments (i.e. ~ 0.1 A). An exception is the intensity ratio I(321.8 A)/I(327.0 A), which appears to provide good estimates of the electron density at this spectral resolution.Comment: 6 pages, 3 figures, Astronomy & Astrophysics, in pres

Can Strong Gravitational Lensing Constrain Dark Energy?

We discuss the ratio of the angular diameter distances from the source to the lens, $D_{ds}$, and to the observer at present, $D_{s}$, for various dark energy models. It is well known that the difference of $D_s$s between the models is apparent and this quantity is used for the analysis of Type Ia supernovae. However we investigate the difference between the ratio of the angular diameter distances for a cosmological constant, $(D_{ds}/D_{s})^{\Lambda}$ and that for other dark energy models, $(D_{ds}/D_{s})^{\rm{other}}$ in this paper. It has been known that there is lens model degeneracy in using strong gravitational lensing. Thus, we investigate the model independent observable quantity, Einstein radius ($\theta_E$), which is proportional to both $D_{ds}/D_s$ and velocity dispersion squared, $\sigma_v^2$. $D_{ds}/D_s$ values depend on the parameters of each dark energy model individually. However, $(D_{ds}/D_s)^{\Lambda} - (D_{ds}/D_{s})^{\rm{other}}$ for the various dark energy models, is well within the error of $\sigma_v$ for most of the parameter spaces of the dark energy models. Thus, a single strong gravitational lensing by use of the Einstein radius may not be a proper method to investigate the property of dark energy. However, better understanding to the mass profile of clusters in the future or other methods related to arc statistics rather than the distances may be used for constraints on dark energy.Comment: 15 pages, 13 figures, Accepted in PR

Glacial and Postglacial History of the White Cloud Peaks-Boulder Mountains, Idaho, U.S.A.

Glacial and glaciofluvial deposits are mapped and differentiated to develop new local, relative-age (RD) stratigraphies for the North Fork of the Big Lost River, Slate Creek and Pole Creek drainages in the White Cloud Peaks and Boulder Mountains, Idaho. This stratigraphic model expands the areal extent of the "Idaho glacial model". Volcanic ash samples collected from the study area are petrographically characterized and correlated, on the basis of mineralogy and glass geochemistry, to reference samples of identified Cascade Range tephras. Four distinct tephras are recognized including; Mount St. Helens-Set S (13,600-13,300 yr BP), Glacier Peak-Set B (11,250 yr BP), Mount Mazama (6600 yr BP) and Mount St. Helens-Set Ye (4350 yr BP). A core of lake sediments containing two tephra units was obtained from a site called "Pole Creek kettle". Pollen and sediment analyses indicate three intervals of late Pleistocene and Holocene climatic change. Cool and wet climatic conditions prevailed in the region shortly before and immediately following the deposition of the Glacier Peak-Set B ash (11,250 yr BP). Climatic warming occurred from approximately 10,500 to 6600 yr BP after which warm, dry conditions prevailed. Sediment accumulation in the kettle ceased by 4350 yr BP. The presence of Glacier Peak-Set B tephra in the base of the Pole Creek kettle core provides a minimum age of 11,250 yr BP for the retreat of valley glaciers from their Late Wisconsinan maximum position. A radiocarbon date of 8450 + 85 yr BP (SI-5181), and the presence of Mount Mazama ash (6600 yr BP) up-core support the Glacier Peak-Set B identification.La cartographie et l'identification des dépôts glaciaires et fluvioglaciaires a permis d'établir la stratigraphie locale des bassins du North Fork de la Big Lost River, du Pole Creek et du Slate Creek. Le modèle stratigraphique établi augmente la superficie déjà couverte par le modèle glaciaire de l'Idaho. Les échantillons de cendre volcanique prélevés ont été identifiés sur le plan pétrographique et mis en corrélation avec des tephras témoins provenant du Cascade Range, en se fondant sur la composition minérale et sur la géochimie du verre. On distingue quatre types de tephras: ceux de la série S du mont St. Helen's (13 600-13 300 BP), ceux de la série B du Glacier Peak (11 250 BP), ceux de la série S du mont St. Helen's (4350 BP) et ceux du mont Mazama (6600 BP). Une carotte de sédiments lacustres prélevée dans le kettle Pole Creek renferme deux tephras. L'analyse du pollen et des sédiments révèle l'existence de trois grands changements climatiques au Pleistocene supérieur et à l'Holocène: un climat frais et humide un peu avant et immédiatement après la mise en place des cendres de la série B du Glacier Peak (11 250 BP); une période de réchauffement (10 500-6600 BP); un climat chaud et sec. L'accumulation de sédiments dans le kettle prit fin vers 4350 BP. La présence du tephra de la série B du Glacier Peak à la base de la carotte donne la date minimale du retrait des glaciers de vallée (11 250 BP) à partir de leur emplacement au Wisconsinien supérieur. La date de 8450 + 85 ans BP et la présence, dans la partie supérieure de la carotte, de cendres provenant du mont Mazama (6600 BP) confirment l'identification de la série B du Glacier Peak.Idaho, U.S.A. Glaziale und glaziofluviale Ablagerungen wurden kartographiert und identifiziert, um eine neue, lokale, relative Alters-Stratigraphie der North Fork des Big Lost River, des Slate Creek und des Pole Creek in den White Cloud Peaks und Boulder Mountains, Idaho, zu en-twickeln. Proben vulkanischer Asche, die im untersuchten Gebiet gesammelt wurden, werden petrographisch bestimmt und auf der Basis von mineralogischer Zusammensetzung und Geochemie des Glases in Wechselbe-ziehung zu Referenz-Belegen von identifi-zierten Tephras von den Cascade Ranges gesetzt. Es werden vier verschiedene Tephras identifiziert: von der Série S des Mount St. Helens (13 600-13 300 v.u.Z.), von der Série B des Glacier Peak (11 250 v.u.Z.), von der Série Ye des Mount Mazama (6600 v.u.Z.) und des Mount St. Helens (4350 v.u.z.). Eine Probe von See-Sedimenten, der vom Pole Creek Kettle gewonnen wurde, enthâlt zwei Tephra-Einheiten. Die Pollen- und Sediment-Analysen lassen drei Intervalle klimatischen Wechsels im spâten Pleistozân und im Ho-lozan erkennen. Kalte und feuchte Klimatische Bedingungen herrschten in diesem Gebiet vor, kurz vor und unmittelbar nach der Ablagerung der Asche der Série B des Glacier Peak (11 250 v.u.Z.). Eine klimatische Erwàrmung trat zwischen ungefàhr 10 500 bis 6600 v.u.Z. auf, nach welcher warme, trockene Bedingungen vorherrschten. Die Sediment-An-hàufung in dem Kettel endete ungefàhr um 4350 v.u.Z. Das Vorkommen von Tephra der Série B des Glacier Peak in der Basis der Probe des Pole Creek Kettle ergibt ein Minimum-Alter von 11 250 v.u.Z. fur den Ruckzug der Gletscher des TaIs von ihrer maximalen Position im spâten Wisconsin. Ein Radiokar-bon-Datum von 8450 + 85 v.u.Z. (SI-5181) und das Vorkommen von Asche des Mount Mazama (6600 v.u.Z.) im oberen Teil der Probe stutzen die Identifizierung der Série B des Glacier Peak

Illustrative components of the geological environment

In this chapter we provide an account of the contribution made by the Geosphere, in particular bedrock geological materials (part of the lithosphere), groundwater and hydrochemistry to the development of a GDF. In order to put this in context we provide a brief account of the general requirements of these attributes, particularly in respect of the post closure safety and, to a lesser extent, the construction phase of the GDF. We also provide a brief summary of the international approach to using bedrock geological materials and go on to describe the summary properties from a range of bedrock geological materials (lithologies and formations) in England, Wales and Northern Ireland, illustrated from well-documented examples

Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS - a collection of Technical Notes Part 1

This report provides an introduction and overview of the Technical Topic Notes (TTNs) produced in the Towards Identifying and closing Gaps in Assurance of autonomous Road vehicleS (Tigars) project. These notes aim to support the development and evaluation of autonomous vehicles. Part 1 addresses: Assurance-overview and issues, Resilience and Safety Requirements, Open Systems Perspective and Formal Verification and Static Analysis of ML Systems. Part 2: Simulation and Dynamic Testing, Defence in Depth and Diversity, Security-Informed Safety Analysis, Standards and Guidelines

Exploring gravitational theories beyond Horndeski

We have recently proposed a new class of gravitational scalar-tensor theories free from Ostrogradski instabilities, in arXiv:1404.6495. As they generalize Horndeski theories, or "generalized" galileons, we call them G$^3$. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they contain only three propagating degrees of freedom by presenting the details of the Hamiltonian formulation. We examine the coupling between these theories and matter. Moreover, we investigate how they transform under a disformal redefinition of the metric. Remarkably, these theories are preserved by disformal transformations that depend on the scalar field gradient, which also allow to map subfamilies of G$^3$ into Horndeski theories.Comment: 33 pages, added comments and corrected typos as in JCAP versio

The Effects of Stacking on the Configurations and Elasticity of Single Stranded Nucleic Acids

Stacking interactions in single stranded nucleic acids give rise to configurations of an annealed rod-coil multiblock copolymer. Theoretical analysis identifies the resulting signatures for long homopolynucleotides: A non monotonous dependence of size on temperature, corresponding effects on cyclization and a plateau in the extension force law. Explicit numerical results for poly(dA) and poly(rU) are presented.Comment: 4 pages and 2 figures. Accepted in Phys. Rev. E Rapid Com