New equipment and processing for magnetotelluric remote reference observations   总被引：2，自引：0，他引：2  

Oliver Ritter  reas Junge  & Graham Dawes 《Geophysical Journal International》1998,132(3):535-548

Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations.  相似文献   

Determining the Sula block kinematics in the triple junction area in Indonesia by GPS   总被引：1，自引：0，他引：1  

Andrea Walpersdorf  Christophe Vigny  P. Manurung  C. Subarya  & S. Sutisna 《Geophysical Journal International》1998,135(2):351-361

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New Definition of Discovery for Solar System Objects     

Andrea Milani  Giovanni F. Gronchi  Zoran Knežević 《Earth, Moon, and Planets》2007,100(1-2):83-116

We propose a new formal definition of discovery for a Solar System object. It is based on an objective and mathematically rigorous algorithm to assess when a set of observations is enough to constitute a discovery. When this definition is satisfied, in almost all cases the orbit is defined well enough to establish the nature of the object discovered (Main Belt vs. Near Earth Asteroid, Trans-Neptunian vs. long period comet). The frequency of occurrence of exceptions is estimated by a set of numerical experiments. The availability of a non-subjective definition of discovery allows some rules to be adopted for the assignment of discovery credit with a minimum risk of dispute. Such rules should be fair, encourage good practice by the observers and acknowledge the contribution of the orbit computers providing the identifications and the orbits, as well as the one of all the contributing observers.  相似文献   

International viewpoint and news     

Andrea Martin  Philip E. LaMoreaux 《Environmental Geology》2007,52(6):1223-1224

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Using XMM-Newton to measure the spectrum of the Vela pulsar and its phase variation     

Armando Manzali  Andrea De Luca  Patrizia A. Caraveo 《Astrophysics and Space Science》2007,308(1-4):601-605

We report on our analysis of two XMM-Newton observations of the Vela pulsar performed in December 2000 (total exposure time: 96.5 ks). We succeeded in resolving the pulsar spectrum from the surrounding bright nebular emission taking advantage both of the accurate calibration of the EPIC point spread function and of the Chandra/HRC surface brightness map of the nebula. This made it possible to assess to pulsar spectral shape disentangling its thermal and non-thermal components. Exploiting the photon harvest, we have also been able to perform a phase-resolved study of the pulsar emission.   相似文献   

Jet Deflection by a Quasi-Steady-State Side Wind in the Laboratory     

David J. Ampleford  Andrea Ciardi  Sergey V. Lebedev  Simon N. Bland  Simon C. Bott  Jeremy P. Chittenden  Gareth N. Hall  Adam Frank  Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34

We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium.  相似文献   

XMM–Newton observations of soft gamma-ray repeaters     

Sandro Mereghetti  Paolo Esposito  Andrea Tiengo 《Astrophysics and Space Science》2007,308(1-4):13-23

All the confirmed Soft Gamma-ray Repeaters have been observed with the EPIC instrument on the XMM–Newton satellite. We review the results obtained in these observations, providing the most accurate spectra on the persistent X-ray emission in the 1–10 keV range for these objects, and discuss them in the context of the magnetar interpretation.   相似文献   

Cosmic stellar relics in the Galactic halo     

Stefania Salvadori  Raffaella Schneider  Andrea Ferrara 《Monthly notices of the Royal Astronomical Society》2007,381(2):647-662

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Entropy profiles in X-ray luminous galaxy clusters at z > 0.1     

Andrea Morandi  Stefano Ettori 《Monthly notices of the Royal Astronomical Society》2007,380(4):1521-1532

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Investigation of groundwater residence times during bank filtration in Berlin: a multi‐tracer approach     

Gudrun Massmann  Jürgen Sültenfuß  Uwe Dünnbier  Andrea Knappe  Thomas Taute  Asaf Pekdeger 《水文研究》2008,22(6):788-801

Berlin relies on induced bank filtration from a broad‐scale, lake‐type surface water system. Because the surface water contains treated sewage, wastewater residues are present in surface water and groundwater. Multiple environmental tracers, including tritium and helium isotopes (³H, ³He, ⁴He), stable isotopes (δ¹⁸O and δ²H) and a number of persistent sewage indicators, such as chloride, boron and a selection of pharmaceutical residues (phenazone‐type analgesics and their metabolites, carbamazepine and anthropogenic gadolinium, Gd_excess), were used to estimate travel times from the surface water to individual production and observation wells at two sites. The study revealed a strong vertical age stratification throughout the upper aquifer, with travel times varying from a few months to several decades in greater depth. Whereas the shallow bank filtrate is characterized by the reflection of the time‐variant tracer input concentrations and young ³H/³He ages, the deeper, older bank filtrate displays no tracer seasonality, ³H/³He ages of a few years to decades and strongly deviating concentrations of several pharmaceutical residues, reflecting concentrations of the source surface water over time. The phenazone‐type pharmaceuticals persist in the aquatic environments for decades. Bank filtration in Berlin is only possible at the sandy lakeshores. In greater water depth, impermeable lacustrine sapropels inhibit infiltration. The young bank filtrate originates from the nearest shore, whereas the older bank filtrate infiltrates at more distant shores. This paper illustrates the importance of using multiple tracer methods, capable of resolving a broad range of residence times, to gain a comprehensive understanding of time‐scales and infiltration characteristics in a bank filtration system. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献