2,554 research outputs found
CAN-HK : An a priori crustal model for the Canadian Shield
ACKNOWLEDGMENTS The United Kingdom component of the Hudson Bay Lithospheric Experiment (HuBLE) was supported by the Natural Environment Research Council (NERC) Grant Number NE/F007337/1, with financial and logistical support from the Geological Survey of Canada (GSC), Canada-Nunavut Geoscience Office (CNGO), SEIS-UK (the seismic node of NERC), and the First Nations communities of Nunavut. J. Beauchesne and J. Kendall provided invaluable assistance in the field. I. D. B. was funded by the Leverhulme Trust and acknowledges support through Grant Number RPG-2013- 332. The authors thank three anonymous reviewers for their constructive comments.Peer reviewedPublisher PD
Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux
The SNO+ detector, a new kiloton scale liquid scintillator detector capable
of recording geoneutrino events, will define the strength of the Earth
radiogenic heat. A detailed 3-D model of the regional crust, centered at SNO+
and based on compiled geological, geophysical and geochemical information, was
used to characterize the physical and chemical attributes of crust and assign
uncertainties to its structure. Monte Carlo simulations were used to predict
the U and Th abundances and uncertainties in crustal lithologies and to model
the regional crustal geoneutrino signal originating from the at SNO+
Expected geoneutrino signal at JUNO
Constraints on the Earth's composition and on its radiogenic energy budget
come from the detection of geoneutrinos. The KamLAND and Borexino experiments
recently reported the geoneutrino flux, which reflects the amount and
distribution of U and Th inside the Earth. The KamLAND and Borexino experiments
recently reported the geoneutrino flux, which reflects the amount and
distribution of U and Th inside the Earth. The JUNO neutrino experiment,
designed as a 20 kton liquid scintillator detector, will be built in an
underground laboratory in South China about 53 km from the Yangjiang and
Taishan nuclear power plants. Given the large detector mass and the intense
reactor antineutrino flux, JUNO aims to collect high statistics antineutrino
signals from reactors but also to address the challenge of discriminating the
geoneutrino signal from the reactor background.The predicted geoneutrino signal
at JUNO is 39.7 TNU, based on the existing reference Earth
model, with the dominant source of uncertainty coming from the modeling of the
compositional variability in the local upper crust that surrounds (out to
500 km) the detector. A special focus is dedicated to the 6{\deg} x
4{\deg} Local Crust surrounding the detector which is estimated to contribute
for the 44% of the signal. On the base of a worldwide reference model for
reactor antineutrinos, the ratio between reactor antineutrino and geoneutrino
signals in the geoneutrino energy window is estimated to be 0.7 considering
reactors operating in year 2013 and reaches a value of 8.9 by adding the
contribution of the future nuclear power plants. In order to extract useful
information about the mantle's composition, a refinement of the abundance and
distribution of U and Th in the Local Crust is required, with particular
attention to the geochemical characterization of the accessible upper crust.Comment: Slight changes and improvements in the text,22 pages, 4 Figures, 3
Tables. Prog. in Earth and Planet. Sci. (2015
Upper limits on the observational effects of nuclear pasta in neutron stars
The effects of the existence of exotic nuclear shapes at the bottom of the
neutron star inner crust - nuclear `pasta' - on observational phenomena are
estimated by comparing the limiting cases that those phases have a vanishing
shear modulus and that they have the shear modulus of a crystalline solid . We
estimate the effect on torsional crustal vibrations and on the maximum
quadrupole ellipticity sustainable by the crust. The crust composition and
transition densities are calculated consistently with the global properties,
using a liquid drop model with a bulk nuclear equation of state (EoS) which
allows a systematic variation of the nuclear symmetry energy. The symmetry
energy J and its density dependence L at nuclear saturation density are the
dominant nuclear inputs which determine the thickness of the crust, the range
of densities at which pasta might appear, as well as global properties such as
the radius and moment of inertia. We show the importance of calculating the
global neutron star properties on the same footing as the crust EoS, and
demonstrate that in the range of experimentally acceptable values of L, the
pasta phase can alter the crust frequencies by up to a factor of three,
exceeding the effects of superfluidity on the crust modes, and decrease the
maximum quadrupole ellipticity sustainable by the crust by up to an order of
magnitude. The signature of the pasta phases and the density dependence of the
symmetry energy on the potential observables highlights the possibility of
constraining the EoS of dense, neutron-rich matter and the properties of the
pasta phases using astrophysical observations.Comment: 8 pages, 7 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Separation of oceanic and continental crustal field signatures using Slepian functions
Models of the crustal magnetic field are typically represented using spherical harmonic coefficients. Rather than spherical harmonics, spherical Slepian functions can be employed to produce a locally and also globally orthogonal basis in which to optimally represent the available data in a region at a given degree. The region can have any arbitrary shape and size. The Slepian functions can be tailored to be either band- or space-limited, allowing a trade-off between spectral and spatial concentration in the region and leakage beyond. Another advantage is that only N Slepian coefficients are required to be solved for to optimally concentrate the energy of the Slepian functions into the region of interest (N = (L+1)2R/4Ï ; where N is the Shannon Number and R is the size of the region as a fraction of the full sphere) .
We use N Slepian functions to optimally separate a crustal field model into its oceanic and continental regions in order to investigate the spectral content of each. Spherical harmonic coefficients are transformed into Slepian coefficients, separated into the appropriate regions and transformed back to spherical harmonic coefficients representing the space-limited extent of the oceans and continents. The spectral power of each region is examined over degrees L = 16-72. We show that both regions display different power levels at discrete bandwidths. For example, the oceanic signal dominates at degrees 16-30, while the continental signal is stronger at degrees 45-65. We compare different crustal models to illustrate that the derived signals are robust
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