共查询到20条相似文献,搜索用时 31 毫秒
1.
N. Tolich Y. -D. Chan C. A. Currat B. K. Fujikawa R. Henning K. T. Lesko A. W. P. Poon M. P. Decowski J. Wang K. Tolich 《Earth, Moon, and Planets》2006,99(1-4):229-240
A significant fraction of the 44TW of heat dissipation from the Earth’s interior is believed to originate from the decays
of terrestrial uranium and thorium. The only estimates of this radiogenic heat, which is the driving force for mantle convection,
come from Earth models based on meteorites, and have large systematic errors. The detection of electron antineutrinos produced
by these uranium and thorium decays would allow a more direct measure of the total uranium and thorium content, and hence
radiogenic heat production in the Earth. We discuss the prospect of building an electron antineutrino detector approximately
700 m3 in size in the Homestake mine at the 4850’ level. This would allow us to make a measurement of the total uranium and thorium
content with a statistical error less than the systematic error from our current knowledge of neutrino oscillation parameters.
It would also allow us to test the hypothesis of a naturally occurring nuclear reactor at the center of the Earth. 相似文献
2.
Sanshiro Enomoto 《Earth, Moon, and Planets》2006,99(1-4):131-146
The Kamioka liquid scintillator antineutrino detector (KamLAND), which consists of 1000 tones of ultra-pure liquid scintillator
surrounded by 1879 photo-multiplier tubes (PMT), is the first detector sensitive enough to detect geoneutrinos. Earth models
suggest that KamLAND observes geoneutrinos at a rate of 30 events/1032-protons/year from the 238U decay chain, and 8 events/1032-protons/year from the 232Th decay chain. With 7.09×1031 proton-years of detector exposure and detection efficiency of 0.687 ± 0.007, the ‘rate-only’ analysis gives geoneutrino candidates. Assuming a Th/U mass concentration ratio of 3.9, the ‘rate + shape’ analysis gives the 90% confidence
interval for the total number of geoneutrinos detected to be from 4.5 to 54.2. This result is consistent with predictions
from the Earth models. The 99% C.L. upper limit is set at 1.45×10−31 events per target proton per year, which is 3.8 times higher than the central value of the model prediction that gives 16 TW
of radiogenic heat production from 238U and 232Th. Although the present data have limited statistical power, they provide by direct means an upper limit for the Earth’s
radiogenic heat of U and Th.
Sanshiro Enomoto (on behalf of the KamLAND Collaboration) 相似文献
3.
Jelena Maricic 《Earth, Moon, and Planets》2006,99(1-4):147-153
A natural nuclear fission reactor operating in the center of the Earth has been proposed by Herndon (Hollenbach and Herndon,
2001) as the energy source that powers the geo-magnetic field. The upper limit on the expected geo-reactor power is set by
the estimated 12 TW (Buffett, 2003) heat flow from the Earth’s core. If it exists, a nuclear reactor of that size emits a
strong anti-neutrino flux. Emitted electron anti-neutrinos can be detected by the Kamioka liquid scintillator anti-neutrino
detector (KamLAND) (Raghavan, 2002), and the geo-reactor power level is proporional to the anti-neutrino emission rate. KamLAND
measures the geo-reactor power as a constant positive offset in detected anti-neutrino rate on top of the varying anti-neutrino
rate coming from man-made reactors. Here we present the first attempt to measure the geo-reactor power. Based on a 776 ton-year
exposure of KamLAND to electron anti-neutrinos, the detected flux corresponds to (6 ± 6) TW. The upper limit on the geo-reactor
power at 90% confidence level is 18 TW, which is below the lower limit of the total Earth’s radiogenic heat, estimated to
be between 19 and 31TW (Anderson, 2003). 相似文献
4.
Ganymede has an intrinsic magnetic field which is generally considered to originate from a self-excited dynamo in the metallic core. Driving of the dynamo depends critically on the satellite's thermal state and internal structure. However, the inferred structure based on gravity data alone has a large uncertainty, and this makes the possibility of dynamo activity unclear; variations in core size and composition significantly change the heat capacity and alter the cooling history of the core. The main objectives of this study is to explore the structural conditions for a currently active dynamo in Ganymede using numerical simulations of the thermal history, and to evaluate under which conditions Ganymede can maintain the dynamo activity at present. We have investigated the satellite's thermal history using various core sizes and compositions satisfying the mean density and moment of inertia of Ganymede, and evaluate the temperature and heat flux at the core-mantle boundary (CMB). Based on the following two conditions, we evaluate the possibility of dynamo activity, thereby reducing the uncertainty of the previously inferred interior structure. The first condition is that the temperature at the CMB must exceed the melting point of a metallic core, and the second is that the heat flux through the CMB must exceed the adiabatic temperature gradient. The mantle temperature starts to increase because of the decay of long-lived radiogenic elements in the rocky mantle. After a few Gyr, radiogenic elements are exhausted and temperature starts to decrease. As the rocky mantle cools, the heat flux at the CMB steadily increases. If the temperature and heat flux at the CMB satisfy these conditions simultaneously, we consider the case as capable of driving a dynamo. Finally, we identify the Dynamo Regime, which is the specific range of internal structures capable of driving the dynamo, based on the results of simulations with various structures. If Ganymede's self-sustained magnetic field were maintained by thermal convection, the satellite's metallic core would be relatively large and, in comparison to other terrestrial-type planetary cores, strongly enriched in sulfur. The dynamo activity and the generation of the magnetic field of Ganymede should start from a much later stage, possibly close to the present. 相似文献
5.
6.
Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a unique probe of the Earth interior. The characterization
of their fluxes is subject, however, to rather large and highly correlated uncertainties. The geochemical covariance of the
U, Th and K abundances in various Earth reservoirs induces positive correlations among the associated geo-neutrino fluxes,
and between these and the radiogenic heat. Mass-balance constraints in the Bulk Silicate Earth (BSE) tend instead to anti-correlate
the radiogenic element abundances in complementary reservoirs. Experimental geo-neutrino observables may be further (anti)correlated
by instrumental effects. In this context, we propose a systematic approach to covariance matrices, based on the fact that
all the relevant geo-neutrino observables and constraints can be expressed as linear functions of the U, Th and K abundances
in the Earth’s reservoirs (with relatively well-known coefficients). We briefly discuss here the construction of a tentative
“geo-neutrino source model” (GNSM) for the U, Th, and K abundances in the main Earth reservoirs, based on selected geophysical
and geochemical data and models (when available), on plausible hypotheses (when possible), and admittedly on arbitrary assumptions
(when unavoidable). We use then the GNSM to make predictions about several experiments (“forward approach”), and to show how
future data can constrain a posteriori the error matrix of the model itself (“backward approach”). The method may provide a useful statistical framework for evaluating
the impact and the global consistency of prospective geo-neutrino measurements and Earth models. 相似文献
7.
O. V. Dudnik P. Podgorski J. Sylwester S. Gburek M. Kowalinski M. Siarkowski S. Plocieniak J. Bakala 《Solar System Research》2012,46(2):160-169
A joint analysis is carried out of data obtained with the help of the solar X-ray SphinX spectrophotometer and the electron
and proton satellite telescope STEP-F in May 2009 in the course of the scientific space experiment CORONAS-PHOTON. In order
to determine the energies and particle types, in the analysis of spectrophotometer records data are used on the intensities
of electrons, protons, and secondary γ-radiation, obtained by the STEP-F telescope, which was located in close proximity to
the SphinX spectrophotometer. The identical reaction of both instruments is noted at the intersection of regions of the Brazilian
magnetic anomaly and the Earth’s radiation belts. It is shown that large area photodiodes, serving as sensors of the X-ray
spectrometer, reliably record electron fluxes of low and intermediate energies, as well as fluxes of the secondary gamma radiation
from construction materials of detector modules, the TESIS instrument complex, and the spacecraft itself. The dynamics of
electron fluxes, recorded by the SphinX spectrophotometer in the vicinity of a weak geomagnetic storm, supplements the information
about the processes of radial diffusion of electrons, which was studied using the STEP-F telescope. 相似文献
8.
A. R. HILDEBRAND K. A. CARROLL E. F. TEDESCO D. R. FABER R. D. CARDINAL J. M. MATTHEWS R. KUSCHNIG G. A. H. WALKER B. GLADMAN J. PAZDER P. G. BROWN S. M. LARSON S. P. WORDEN B. J. WALLACE P. W. CHODAS K. MUINONEN A. CHENG 《Earth, Moon, and Planets》2004,95(1-4):33-40
Space-based observatories have several advantages over ground-based observatories in searching for asteroids and comets. In
particular, the Aten and Interior to Earth’s Orbit (IEO) asteroid classes may be efficiently sought at low solar elongations
along the ecliptic plane. A telescope in low Earth orbit has a sufficiently long orbital baseline to determine the parallax
for all Aten and IEO class asteroids discovered with this observing strategy. The Near Earth Object Space Surveillance Satellite
(NEOSSat) mission will launch a microsatellite to exploit this observing strategy complementing ground-based search programmes. 相似文献
9.
In this paper, two factors — the redistribution of the density and the variation in the angular velocity of the Earth rotation, that affect the adopted value of the flattening for equidensity surface within the Earth, are discussed. The computational results show that the contribution of the redistribution of the density in the Earth interior (especially in the core) on the change of the flattening at the core-mantle boundary (CMB) is marginal, and that the calculated value of the flattening at the CMB can be in good agreement with the VLBI observed value so long as the fact that the angular velocity of the Earth rotation has undergone the tidal evolution is taken into account. As a result, this paper presents a set of recommended values of the dynamical parameters of the Earth (see Table III) for computing Earth's forced nutation series. 相似文献
10.
Kathrin A. Hochmuth Franz V. Feilitzsch Teresa Marrodán Undagoitia Lothar Oberauer Walter Potzel Michael Wurm Brian D. Fields 《Earth, Moon, and Planets》2006,99(1-4):253-264
A future large-volume liquid scintillator detector such as the proposed 50 kton LENA (Low Energy Neutrino Astronomy) detector
would provide a high-statistics measurement of terrestrial antineutrinos originating from β-decays of the uranium and thorium
chains. Additionally, the neutron is scattered in the forward direction in the detection reaction . Henceforth, we investigate to what extent LENA can distinguish between certain geophysical models on the basis of the angular
dependence of the geoneutrino flux. Our analysis is based on a Monte-Carlo simulation with different levels of light yield,
considering an unloaded PXE scintillator. We find that LENA is able to detect deviations from isotropy of the geoneutrino
flux with high significance. However, if only the directional information is used, the time required to distinguish between
different geophysical models is of the order of severals decades. Nonetheless, a high-statistics measurement of the total
geoneutrino flux and its spectrum still provides an extremely useful glance at the Earth’s interior. 相似文献
11.
Mikhail Batygov 《Earth, Moon, and Planets》2006,99(1-4):183-192
The possibility of terrestrial antineutrino directionality studies is considered for future unloaded liquid scintillator detectors.
Monte-Carlo simulations suggest that the measurable displacement between prompt and delayed antineutrino signals makes such
studies possible. However, it is estimated that on the order of 1000 terrestrial antineutrino events are required to test
the simplest models, demanding detectors of 100 kt size to collect sufficient data in a reasonable period of time. 相似文献
12.
Using 1.55cm observations of the Earth made by the Electrically Scanned Microwave Radiometer experiment on Nimbus 5, the appearance of the Earth from Venus is simulated. A single antenna unable to resolve the Earth's disk would give a time averaged disk temperature of 183K. In one rotation, the disk temperature would vary from 194K to 172K. During the 1973 inferior conjunction, a radio telescope with 1 arcsec resolution would resolve most of the major surface features of the Earth. 相似文献
13.
R.D. Schuiling 《Earth, Moon, and Planets》2006,99(1-4):33-49
In this paper we discuss the Herndon hypothesis that a nuclear reactor is operating at the center of the Earth. Recent experimental
evidence shows that some uranium can have partitioned into the core. There is no viable mechanism for the small amount of
uranium that is dissolved in the molten metal to crystallize as a separate uranium phase (uranium metal or uranium sulfide)
and migrate to the center of the core.
There is no need for an extra heat source, as the total heat leaving the core can be easily provided by “classical” heat sources,
which are also more than adequate to maintain the Earth’s magnetic field. It is unlikely that nuclear georeactors (fast breeder
reactors) are operating at the Earth’s center. 相似文献
14.
Walter Winter 《Earth, Moon, and Planets》2006,99(1-4):285-307
Because the propagation of neutrinos is affected by the presence of Earth matter, it opens new possibilities to probe the
Earth’s interior. Different approaches range from techniques based upon the interaction of high energy (above TeV) neutrinos
with Earth matter, to methods using the MSW effect on the oscillations of low energy (MeV to GeV) neutrinos. In principle,
neutrinos from many different sources (sun, atmosphere, supernovae, beams etc.) can be used. In this talk, we summarize and
compare different approaches with an emphasis on more recent developments. In addition, we point out other geophysical aspects
relevant for neutrino oscillations. 相似文献
15.
We present results of simulations performed with the Geant4 software code of the effects of Galactic Cosmic Ray impacts on
the photoconductor arrays of the PACS instrument. This instrument is part of the ESA-Herschel payload, which will be launched
in 2008 and will operate at the Lagrangian L2 point of the Sun-Earth system. Both the Satellite plus the cryostat (the shield)
and the detector act as source of secondary events, affecting the detector performance. Secondary event rates originated within
the detector and from the shield are of comparable intensity. The impacts deposit energy on each photoconductor pixel but
do not affect the behaviour of nearby pixels. These latter are hit with a probability always lower than 7%.
The energy deposited produces a spike which can be hundreds times larger than the noise. We then compare our simulations with
proton irradiation tests carried out for one of the detector modules and follow the detector behaviour under ‘real’ conditions. 相似文献
16.
Cherenkov telescopes have the capability of detecting high energy tau neutrinos in the energy range of 1–1000 PeV by searching for very inclined showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth or a mountain, it will decay and initiate a shower in the air which can be detected by an air shower fluorescence or Cherenkov telescope. In this paper, we present detailed Monte Carlo simulations of corresponding event rates for the VERITAS and two proposed Cherenkov Telescope Array sites: Meteor Crater and Yavapai Ranch, which use representative AGN neutrino flux models and take into account topographic conditions of the detector sites. The calculated neutrino sensitivities depend on the observation time and the shape of the energy spectrum, but in some cases are comparable or even better than corresponding neutrino sensitivities of the IceCube detector. For VERITAS and the considered Cherenkov Telescope Array sites the expected neutrino sensitivities are up to factor 3 higher than for the MAGIC site because of the presence of surrounding mountains. 相似文献
17.
Peter von Ballmoos Jose Alvarez Nicolas Barrière Steve Boggs Andrei Bykov Juan Manuel Del Cura Velayos Filippo Frontera Lorraine Hanlon Margarita Hernanz Emmanuel Hinglais Jordi Isern Pierre Jean Jürgen Kn?dlseder Lucien Kuiper Mark Leising Beno?t Pirard Jean-Pierre Prost Rui M. Curado da Silva Tadayuki Takahashi John Tomsick Roland Walter Andreas Zoglauer 《Experimental Astronomy》2012,34(2):583-622
DUAL will study the origin and evolution of the elements and explores new frontiers of physics: extreme energies that drive powerful stellar explosions and accelerate particles to macroscopic energies; extreme densities that modify the laws of physics around the most compact objects known; and extreme fields that influence matter in a way that is unknown on Earth. The variability of these extreme objects requires continuous all-sky coverage, while detailed study demands an improvement in sensitivity over previous technologies by at least an order of magnitude. The DUAL payload is composed of an All-Sky Compton Imager (ASCI), and two optical modules, the Laue-Lens Optic (LLO) and the Coded-Mask Optic (CMO). The ASCI serves dual roles simultaneously, both as an optimal focal-plane sensor for deep observations with the optical modules and as a sensitive true all-sky telescope in its own right for all-sky surveys and monitoring. While the optical modules are located on the main satellite, the All-Sky Compton Imager is situated on a deployable structure at a distance of 30?m from the satellite. This configuration not only permits to maintain the less massive payload at the focal distance, it also greatly reduces the spacecraft-induced detector background, and, above all it provides ASCI with a continuous all-sky exposure. 相似文献
18.
The possibility of using a trap with ultracold neutrons as a detector of dark matter particles with long-range forces is considered.
The main advantage of the proposed method lies in the possibility of detecting a recoil energy of ∼10−7 eV. Constraints on the parameters of an interaction potential of the form φ (r) = ae
−r/b
/r between dark matter particles and a neutron are presented at various dark matter densities on Earth. The assumption about
the long-range interaction of dark matter particles and ordinary matter is shown to lead to a significant increase in the
elastic scattering cross section at low energies. As a consequence, it becomes possible to capture and accumulate dark matter
in the Earth’s gravitational field. The accumulated dark matter in the Earth’s gravitational field is roughly estimated. The
first experimental constraints on the existence of dark matter with long-range forces on Earth are presented. 相似文献
19.
K. Jędrzejczak M. Kasztelan L. Mankiewicz M. Molak K. Nawrocki L. W. Piotrowski M. Sokołowski B. Szabelska J. Szabelski T. Wibig A. W. Wolfendale G. Wrochna 《Astrophysics and Space Science》2007,309(1-4):471-475
It is possible that violent processes resulting in Gamma Ray Bursts produce also high energy photons and cosmic rays. The
possible correlations of very short GRB with, e.g., CMB, cosmic rays is briefly discussed. We have also begun preparation
of the experiment correlating in real time data from Maze cosmic ray detector and Pi of the Sky robotic telescope. 相似文献
20.
Marianne Greff-Lefftz Laurent Métivier Hilaire Legros 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):113-146
Tidal forces acting on the Earth cause deformations and mass redistribution inside the planet involving surface motions and
variation in the gravity field, which may be observed in geodetic experiments. Because for space geodesy it is now necessary
to achieve the mm level in tidal displacements, we take into account the hydrostatic flattening of the Earth in the computation
of the elasto-gravitational deformations. Analytical solutions are derived for the semi-diurnal tides on a slightly elliptical
homogeneous incompressible elastic model. That simple analytical Earth’s model is not a realistic representation of any real
planet, but it is useful to understand the physics of the problem and also to check numerical procedures. We rediscover and
discuss the Love’s solutions and obtain new analytical solutions for the tangential displacement. We extend these analytical
results to some geodetic responses of the Earth to tidal forces such as the perturbation of the surface gravity field, the
tilt and the deviation of the vertical with reference to the Earth’s axis. 相似文献