From Gigahertz to Millihertz: A Multiwavelength Study of the Acoustically Active 14 August 2004 M7.4 Solar Flare     

J. C. Martínez-Oliveros  H. Moradi  D. Besliu-Ionescu  A.-C. Donea  P. S. Cally  C. Lindsey 《Solar physics》2007,245(1):121-139

We carried out an electromagnetic acoustic analysis of the solar flare of 14 August 2004 in active region AR10656 from the radio to the hard X-ray spectrum. The flare was a GOES soft X-ray class M7.4 and produced a detectable sun quake, confirming earlier inferences that relatively low energy flares may be able to generate sun quakes. We introduce the hypothesis that the seismicity of the active region is closely related to the heights of coronal magnetic loops that conduct high-energy particles from the flare. In the case of relatively short magnetic loops, chromospheric evaporation populates the loop interior with ionised gas relatively rapidly, expediting the scattering of remaining trapped high-energy electrons into the magnetic loss cone and their rapid precipitation into the chromosphere. This increases both the intensity and suddenness of the chromospheric heating, satisfying the basic conditions for an acoustic emission that penetrates into the solar interior.  相似文献   

Influence of fracture anisotropy on ground water ages and chemistry,Valley and Ridge province,Pennsylvania   总被引：5，自引：0，他引：5  

Burton WC  Plummer LN  Busenberg E  Lindsey BD  Gburek WJ 《Ground water》2002,40(3):242-257

Model ground water ages based on chlorofluorocarbons (CFCs) and tritium/helium-3 (³H/³He) data were obtained from two arrays of nested piezometers located on the north limb of an anticline in fractured sedimentary rocks in the Valley and Ridge geologic province of Pennsylvania. The fracture geometry of the gently east plunging fold is very regular and consists predominately of south dipping to subhorizontal to north dipping bedding-plane parting and east striking, steeply dipping axial-plane spaced cleavage. In the area of the piezometer arrays, which trend north-south on the north limb of the fold, north dipping bedding-plane parting is a more dominant fracture set than is steeply south dipping axial-plane cleavage. The dating of ground water from the piezometer arrays reveals that ground water traveling along paths parallel to the dip direction of bedding-plane parting has younger ³H/³He and CFC model ages, or a greater component of young water, than does ground water traveling along paths opposite to the dip direction. In predominantly unmixed samples there is a strong positive correlation between age of the young fraction of water and dissolved sodium concentration. The travel times inferred from the model ages are significantly longer than those previously calculated by a ground water flow model, which assumed isotropically fractured layers parallel to topography. A revised model factors in the directional anisotropy to produce longer travel times. Ground water travel times in the watershed therefore appear to be more influenced by anisotropic fracture geometry than previously realized. This could have significant implications for ground water models in other areas underlain by similarly tilted or folded sedimentary rock, such as elsewhere in the Valley and Ridge or the early Mesozoic basins.  相似文献   

Helioseismic analysis of the solar flare-induced sunquake of 2005 January 15   总被引：1，自引：0，他引：1  

H. Moradi  A.-C. Donea  C. Lindsey  D. Besliu-Ionescu  P. S. Cally 《Monthly notices of the Royal Astronomical Society》2007,374(3):1155-1163

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On the evolutionary time scale of the accreting component in massive close binaries     

C. Doom  J. P. De Grève 《Astrophysics and Space Science》1981,80(2):369-395

The remaining core hydrogen burning lifetime after mass exchange is computed for the mass gaining component in massive close binary systems. Results are obtained for various modes of mass accretion, for a wide range of initial masses and mass ratios, and for different values of mass loss from the system. The effect of mass loss by stellar wind is included. By use of general properties of massive close binary evolution, the position in time of four events is determined: the end of core hydrogen burning of the primary and the secondary, and the occurrence of the supernova of the primary and the secondary. It is found that the two supernova event occur rather close in time, compared to the Main Sequence time scales of the components.This research is supported by the National Foundation of Collective Fundamental Research of Belgium (FKFO) under No. 2.9009.79.  相似文献   

Community Development Finance Institutions (CDFIs): Geographies of financial inclusion in the US and UK     

Lindsey Appleyard 《Geoforum》2011,42(2):250-258

The financial exclusion of enterprise is a concept that has been largely neglected by economic geographers. This is surprising given the attention dedicated to personal financial exclusion and alternative sources of finance. This paper compares financial inclusion policies in deprived areas of the United States (US) and United Kingdom (UK) through the example of Community Development Finance Institutions (CDFIs). CDFIs help overcome financial exclusion by providing local sources of loan finance to micro, small-and-medium-sized enterprises and social enterprises. Drawing upon interviews with key actors within the CDFI sector in the US and UK respectively, the paper aims to compare the CDFI landscape across the US and UK through the provision of finance for enterprise. This is in order to understand the geographies of finance that are being created by such alternative financial institutions thereby contributing to financial inclusion debates. The research concludes that although CDFIs do provide an important source of finance to excluded enterprises, policy initiatives have created uneven geographical coverage and market gaps leaving marked spaces of financial exclusion.  相似文献   

Comments on V505 mon: One of the most massive binaries     

J. P. De Greve  C. Doom  P. Hellings  W. Packet  R. Stagni  A. Mammano 《Astrophysics and Space Science》1983,95(1):215-217

From a discussion of the results or V505 Mon, we conclude that the spectral types contradict other parameters in the HR diagram.  相似文献   

Modeling global impact effects on middle-sized icy bodies: applications to Saturn's moons     

Lindsey S Bruesch  Erik Asphaug 《Icarus》2004,168(2):457-466

Disrupted terrains that form as a consequence of giant impacts may help constrain the internal structures of planets, asteroids, comets and satellites. As shock waves and powerful seismic stress waves propagate through a body, they interact with the internal structure in ways that may leave a characteristic impression upon the surface. Variations in peak surface velocity and tensile stress, related to landform degradation and surface rupture, may be controlled by variations in core size, shape and density. Caloris Basin on Mercury and Imbrium Basin on the Moon have disturbed terrain at their antipodes, where focusing is most intense for an approximately symmetric spheroid. Although, the icy saturnian satellites Tethys, Mimas, and Rhea possess giant impact structures, it is not clear whether these structures have correlated disrupted terrains, antipodal or elsewhere. In anticipation of high-resolution imagery from Cassini, we investigate antipodal focusing during giant impacts using a 3D SPH impact model. We first investigate giant impacts into a fiducial 1000 km diameter icy satellite with a variety of core radii and compositions. We find that antipodal disruption depends more on core radius than on core density, suggesting that core geometry may express a surface signature in global impacts on partially differentiated targets. We model Tethys, Mimas, and Rhea according to their image-derived shapes (triaxial for Tethys and Mimas and spherical for Rhea), varying core radii and densities to give the proper bulk densities. Tethys shows greater antipodal values of peak surface velocity and peak surface tensile stress, indicating more surface damage, than either Mimas or Rhea. Results for antipodal and global fragmentation and terrain rupture are inconclusive, with the hydrocode itself producing global disruption at the limits of model resolution but with peak fracture stresses never exceeding the strength of laboratory ice.  相似文献   

The lifetimes of sunspot moats     

Lindsey Pardon  Simon P. Worden  Timothy J. Schneeberger 《Solar physics》1979,61(2):247-250

In the standard model of the solar convective zone, turbulent eddies transport entropy rather than temperature. We consider the turbulent mean field equations for the convective zone, including entropy transport, and show that the zone can be unstable to larger scale motion which we identify with the supergranulation and giant cells.  相似文献   

A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology          下载免费PDF全文

Maarten Van Daele  Jasper Moernaut  Lindsey Doom  Evelien Boes  Karen Fontijn  Katrien Heirman  Willem Vandoorne  Dierk Hebbeln  Mario Pino  Roberto Urrutia  Robert Brümmer  Marc De Batist 《Sedimentology》2015,62(5):1466-1496

Seismically‐induced event deposits embedded in the sedimentary infill of lacustrine basins are highly useful for palaeoseismic reconstructions. Recent, well‐documented, great megathrust earthquakes provide an ideal opportunity to calibrate seismically‐induced event deposits for lakes with different characteristics and located in different settings. This study used 107 short sediment cores to investigate the sedimentary impact of the 1960 M_w 9·5 Valdivia and the 2010 M_w 8·8 Maule earthquakes in 17 lakes in South‐Central Chile (i.e. lakes Negra, Lo Encañado, Aculeo, Vichuquén, Laja, Villarrica, Calafquén, Pullinque, Pellaifa, Panguipulli, Neltume, Riñihue, Ranco, Maihue, Puyehue, Rupanco and Llanquihue). A combination of image analysis, magnetic susceptibility and grain‐size analysis allows identification of five types of seismically‐induced event deposits: (i) mass‐transport deposits; (ii) in situ deformations; (iii) lacustrine turbidites with a composition similar to the hemipelagic background sediments (lacustrine turbidites type 1); (iv) lacustrine turbidites with a composition different from the background sediments (lacustrine turbidites type 2) and (v) megaturbidites. These seismically‐induced event deposits were compared to local seismic intensities of the causative earthquakes, eyewitness reports, post‐earthquake observations, and vegetation and geomorphology of the catchment and the lake. Megaturbidites occur where lake seiches took place. Lacustrine turbidites type 2 can be the result of: (i) local near‐shore mass wasting; (ii) delta collapse; (iii) onshore landslides; (iv) debris flows or mudflows; or (v) fluvial reworking of landslide debris. On the contrary, lacustrine turbidites type 1 are the result of shallow mass wasting on sublacustrine slopes covered by hemipelagic sediments. Due to their more constrained origin, lacustrine turbidites type 1 are the most reliable type of seismically‐induced event deposits in quantitative palaeoseismology, because they are almost exclusively triggered by earthquake shaking. Moreover, they most sensitively record varying seismic shaking intensities. The number of lacustrine turbidites type 1 linearly increases with increasing seismic intensity, starting with no lacustrine turbidites type 1 at intensities between V½ and VI and reaching 100% when intensities are higher than VII½. Combining different types of seismically‐induced event deposits allows the reconstruction of the complete impact of an earthquake.  相似文献   

Magneto-Acoustic Energetics Study of the Seismically Active Flare of 15 February 2011     

J. D. Alvarado-Gómez  J. C. Buitrago-Casas  J. C. Martínez-Oliveros  C. Lindsey  H. Hudson  B. Calvo-Mozo 《Solar physics》2012,280(2):335-345

Multi-wavelength studies of energetic solar flares with seismic emissions have revealed interesting common features between them. We studied the first GOES X-class flare of Solar Cycle 24, as detected by the Solar Dynamics Observatory (SDO). For context, seismic activity from this flare (SOL2011-02-15T01:55-X2.2, in NOAA AR 11158) has been reported by Kosovichev (Astrophys. J. Lett., 734, L15, 2011) and Zharkov et?al. (Astrophys. J. Lett., 741, L35, 2011). Based on Dopplergram data from the Helioseismic and Magnetic Imager (HMI), we applied standard methods of local helioseismology in order to identify the seismic sources in this event. RHESSI hard X-ray data are used to check the correlation between the location of the seismic sources and the particle-precipitation sites in during the flare. Using HMI magnetogram data, the temporal profile of fluctuations in the photospheric line-of-sight magnetic field is used to estimate the magnetic-field change in the region where the seismic signal was observed. This leads to an estimate of the work done by the Lorentz-force transient on the photosphere of the source region. In this instance, this is found to be a significant fraction of the acoustic energy in the attendant seismic emission, suggesting that Lorentz forces can contribute significantly to the generation of sunquakes. However, there are regions in which the signature of the Lorentz force is much stronger, but from which no significant acoustic emission emanates.  相似文献