Automated Detection of Coronal Loops using a Wavelet Transform Modulus Maxima Method

We propose and test a wavelet transform modulus maxima method for the au- tomated detection and extraction of coronal loops in extreme ultraviolet images of the solar corona. This method decomposes an image into a number of size scales and tracks enhanced power along each ridge corresponding to a coronal loop at each scale. We compare the results across scales and suggest the optimum set of parameters to maximise completeness while minimising detection of noise. For a test coronal image, we compare the global statistics (e.g., number of loops at each length) to previous automated coronal-loop detection algorithms

Twisting Flux Tubes as a cause of Micro-Flaring Activity

High-cadence optical observations of an H-alpha blue-wing bright point near solar AR NOAA 10794 are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system, the Rapid Dual Imager. Wavelet analysis is undertaken to search for intensity-related oscillatory signatures, and periodicities ranging from 15 to 370 s are found with significance levels exceeding 95%. During two separate microflaring events, oscillation sites surrounding the bright point are observed to twist. We relate the twisting of the oscillation sites to the twisting of physical flux tubes, thus giving rise to reconnection phenomena. We derive an average twist velocity of 8.1 km/s and detect a peak in the emitted flux between twist angles of 180 and 230 degrees.Comment: 8 pages, 10 figure

Relationship between Hard and Soft X-ray Emission Components of a Solar Flare

X-ray observations of solar flares routinely reveal an impulsive high-energy and a gradual low-energy emission component, whose relationship is one of the key issues of solar flare study. The gradual and impulsive emission components are believed to be associated with, respectively, the thermal and nonthermal components identified in spectral fitting. In this paper, a prominent about 50 second hard X-ray (HXR) pulse of a simple GOES class C7.5 flare on 20 February 2002 is used to study the association between high energy, non-thermal and impulsive evolution, and low energy, thermal and gradual evolution. We use regularized methods to obtain time derivatives of photon fluxes to quantify the time evolution as a function of photon energy, obtaining a break energy between impulsive and gradual behavior. These break energies are consistent with a constant value of about 11 keV in agreement with those found spectroscopically between thermal and non-thermal components, but the relative errors of the former are greater than 15% and much greater than the a few percent errors found from the spectral fitting. These errors only weakly depend on assuming an underlying spectral model for the photons, pointing to the current data being inadequate to reduce the uncertainties rather than there being a problem associated with an assumed model. The time derivative method is used to test for the presence of a 'pivot energy' in this flare. Although these pivot energies are marginally consistent with a constant value of about 9 keV, its values in the HXR rise phase appear to be lower than those in the decay phase

Hyperplasia and Fluid Accumulation in Epithelial Cyst Formation and Growth

Epithelial cysts may develop in virtually any epithelium. All cysts, regardless of their origins, are characterized by epithelial hyperplasia and fluid accumulation. Additional features may include tubular atrophy, basement membrane alterations and association with inflammatory cells. In spite of the intense research effort in recent years directed at uncovering the cellular mechanisms of cyst development and growth, we still do not know the primary events that lead to cyst formation. However, there are at least three candidate mechanisms. These include: 1) increased cell proliferation (epithelial hyperplasia) in the cyst wall, 2) net fluid accumulation in the cyst cavity and 3) alterations of extracellular matrix components linked to cyst formation and growth. This review discusses the evidence to support the role of each mechanism as a possible primary event necessary for cyst initiation and continued enlargement. Present data on the pathogenesis of epithelial cyst formation strongly suggests that no single mechanism, as yet described, can adequately account for all situations of cyst occurrence

Discovery of spatial periodicities in a coronal loop using automated edge-tracking algorithms

A new method for automated coronal loop tracking, in both spatial and temporal domains, is presented. Applying this technique to TRACE data, obtained using the 171 Å filter on 1998 July 14, we detect a coronal loop undergoing a 270 s kink-mode oscillation, as previously found by Aschwanden et al. However, we also detect flare-induced, and previously unnoticed, spatial periodicities on a scale of 3500 km, which occur along the coronal loop edge. Furthermore, we establish a reduction in oscillatory power for these spatial periodicities of 45% over a 222 s interval. We relate the reduction in detected oscillatory power to the physical damping of these loop-top oscillations

On factorizing FF-matrices in Y(sln)Y(sl_n) and Uq(sln^)U_q(\hat{sl_n}) spin chains

We consider quantum spin chains arising from $N$-fold tensor products of the fundamental evaluation representations of $Y(sl_n)$ and $U_q(\hat{sl_n})$. Using the partial $F$-matrix formalism from the seminal work of Maillet and Sanchez de Santos, we derive a completely factorized expression for the $F$-matrix of such models and prove its equivalence to the expression obtained by Albert, Boos, Flume and Ruhlig. A new relation between the $F$-matrices and the Bethe eigenvectors of these spin chains is given.Comment: 30 page

The role of the family in resettlement

This practitioner’s guide unpicks different interpretations of ‘family’. It explores the family’s unique position to fulfil key characteristics that research has shown are associated with effective resettlement support. It highlights recommendations and considerations that can be adopted into the practices of those working with young people and their families. As well as outlining various ways that families can help with personal and structural support, the guide also provides tips for successfully engaging with family members and sets out ways of overcoming the challenges that exist to unlocking this important resource

The Influence of Magnetic Field on Oscillations in the Solar Chromosphere

Two sequences of solar images obtained by the Transition Region and Coronal Explorer in three UV passbands are studied using wavelet and Fourier analysis and compared to the photospheric magnetic flux measured by the Michelson Doppler Interferometer on the Solar Heliospheric Observatory to study wave behaviour in differing magnetic environments. Wavelet periods show deviations from the theoretical cutoff value and are interpreted in terms of inclined fields. The variation of wave speeds indicates that a transition from dominant fast-magnetoacoustic waves to slow modes is observed when moving from network into plage and umbrae. This implies preferential transmission of slow modes into the upper atmosphere, where they may lead to heating or be detected in coronal loops and plumes.Comment: 8 pages, 6 figures (4 colour online only), accepted for publication in The Astrophysical Journa