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Mapping Mercury's internal magnetic field with a magnetometer in closed orbit around the planet will provide valuable information about its internal structure. By measuring magnetic field multipoles of order higher than the dipole we could, in principle, determine some properties, such as size and location, of the internal source. Here we try to quantify these expectations. Using conceptual models, we simulate the actual measurement during the BepiColombo mission, and then we analyze the simulated data in order to estimate the measurement errors due to the limited spatial sampling. We also investigate our ability to locate the field generating current system within the planet. Finally, we address the main limitation of our model, due to the presence of time-varying external magnetospheric currents. 相似文献
74.
The Compton-Getting effect relates the distribution function of a particle population in a given frame of reference to that in another frame, moving at constant velocity V relative to the first. In this note we examine the effects that arise when, contrary to previous assumptions (a) second order terms in ( V/v), where v is the particle velocity, are retained, and (b) when the given distribution function is not isotropic. The importance of the extra terms is then examined in the specific case of low energy solar protons in interplanetary space. 相似文献
75.
I. K. Baldry M. L. Balogh R. G. Bower K. Glazebrook R. C. Nichol S. P. Bamford T. Budavari 《Monthly notices of the Royal Astronomical Society》2006,373(2):469-483
We analyse a z < 0.1 galaxy sample from the Sloan Digital Sky Survey focusing on the variation in the galaxy colour bimodality with stellar mass and projected neighbour density Σ, and on measurements of the galaxy stellar mass functions. The characteristic mass increases with environmental density from about 1010.6 to (Kroupa initial mass function, H 0 = 70 ) for Σ in the range 0.1–10 Mpc−2 . The galaxy population naturally divides into a red and blue sequence with the locus of the sequences in colour–mass and colour–concentration indices not varying strongly with environment. The fraction of galaxies on the red sequence is determined in bins of 0.2 in log Σ and bins). The red fraction f r generally increases continuously in both Σ and such that there is a unified relation: . Two simple functions are proposed which provide good fits to the data. These data are compared with analogous quantities in semi-analytical models based on the Millennium N -body simulation: the Bower et al. and Croton et al. models that incorporate active galactic nucleus feedback. Both models predict a strong dependence of the red fraction on stellar mass and environment that is qualitatively similar to the observations. However, a quantitative comparison shows that the Bower et al. model is a significantly better match; this appears to be due to the different treatment of feedback in central galaxies. 相似文献
76.
János Balogh 《GeoJournal》1995,36(2-3):251-254
The magnetostratigraphical study of Hungarian loesses has been going on for several decades. In spite of a number of attempts, partly in international cooperation, we could not find reversals within the Brunhes Epoch. This is unambiguously associated with the particular characteristics of loess formation and with the relatively short duration of paleomagnetic intervals within this epoch.On the basis of magnetic measurements in the paleosols of the comprehensively studied Basaharc loess profile and presenting the Hódmezövásárhely profile analysed by P. Márton (1979), the application of the paleomagnetic methods for stratigraphic subdivision is presented. This relies on the evaluation of random fluctuations of and tendencies in inclination and declination, of values substantially deviating from the normal but showing no reversal. It is to the purpose to apply this method in conjunction with thermoluminescence chronological techniques. 相似文献
77.
I. G. McCarthy R. G. Bower M. L. Balogh 《Monthly notices of the Royal Astronomical Society》2007,377(4):1457-1463
The universal baryonic mass fraction (Ωb /Ωm ) can be sensitively constrained using X-ray observations of galaxy clusters. In this paper, we compare the baryonic mass fraction inferred from measurements of the cosmic microwave background with the gas mass fractions ( f gas ) of a large sample of clusters taken from the recent literature. In systems cooler than 4 keV, f gas declines as the system temperature decreases. However, in higher temperature systems, f gas ( r 500 ) converges to ≈(0.12 ± 0.02)( h /0.72)−1.5 , where the uncertainty reflects the systematic variations between clusters at r 500 . This is significantly lower than the maximum-likelihood value of the baryon fraction from the recently released Wilkinson Microwave Anisotropy Probe ( WMAP ) 3-yr results. We investigate possible reasons for this discrepancy, including the effects of radiative cooling and non-gravitational heating, and conclude that the most likely solution is that Ωm is higher than the best-fitting WMAP value (we find Ωm = 0.36+0.11 −0.08 ), but consistent at the 2σ level. Degeneracies within the WMAP data require that σ8 must also be greater than the maximum likelihood value for consistency between the data sets. 相似文献
78.
Historical trace metal loading to a large river recorded in the sediments of Lake St. Croix,USA 总被引：1，自引：0，他引：1
Steven J. Balogh Laura D. Triplett Daniel R. Engstrom Yabing H. Nollet 《Journal of Paleolimnology》2010,44(2):517-530
The global cycling of anthropogenic trace metals intensified during the twentieth century, impacting aquatic systems throughout
the world. There are, however, few quantitative records showing the history of this contamination in large rivers. Here we
present a well-dated sedimentary record of trace metal accumulation in Lake St. Croix, a natural riverine lake on the St.
Croix River (Minnesota and Wisconsin, USA), revealing the history of heavy metal inputs to the river over the past 200 years.
Concentrations of Hg, Pb, Ag, Cd, Cr and Zn and stable Pb isotopes were measured in eight 210Pb-dated sediment cores collected from profundal depositional areas throughout the lake. Time trends of trace metal concentrations
and accumulation rates differed greatly between the upper lake (above Valley Creek) and the lower lake, reflecting contrasting
sediment sources along the flow axis of the lake. For most of the study period (1800–2000 AD), sediment deposited throughout
the lake derived almost exclusively from the suspended sediment load carried by the main-stem river into the lake. From 1910
through 1970, however, large inputs of eroded soils and stream channel sediments from side-valley tributaries resulted in
greatly increased sediment and trace metal accumulation in the lower lake. Anthropogenic accumulation rates of Hg, Pb, Cd,
Zn, and Ag in the upper lake correlate well with those from Square Lake, a small, relatively undisturbed nearby lake that
has received trace metal inputs almost exclusively via atmospheric deposition. The similarity of these records suggests that
atmospheric deposition was primarily responsible for trace metal accumulation trends in upper Lake St. Croix. Trace metal
accumulation in the lower lake was also strongly influenced by atmospherically derived inputs, but metal contributions from
native soils were important, as well, during the period of elevated sediment inputs from side-valley tributaries. Concentrations
and accumulation rates of trace metals in both upper and lower lake sediments have decreased substantially since the 1970s
due to decreased atmospheric inputs and sediment loadings, but accumulation rates remain well above pre-settlement values.
Metal inputs to Lake St. Croix have been far lower than those to nearby Lake Pepin, located on the Mississippi River downstream
of the Minneapolis-St. Paul metropolitan area, but there nevertheless remains a clear record of anthropogenic impact on the
relatively pristine St. Croix River. 相似文献
79.
D.J. Southwood M.K. Dougherty P. Canu A. Balogh P.J. Kellogg 《Planetary and Space Science》1993,41(11-12)
The spacecraft Ulysses flew through the Jovian magnetosphere during February 1992. This paper compares the magnetic field observations recorded during the inbound pass of the flyby with the electron density as derived from the URAP instrument. In general, it is expected that the density variations will anti-correlate with the magnetic field strength in order to maintain pressure balance, although there may be instances when a temperature or energy rise alone could balance the static stress. Furthermore, there is the possibility that a dynamic process could occur which would cause both the density and field magnitude to rise in unison. In the middle magnetosphere, anti-correlation is found to exist between the two data sets; however, in the outer magnetosphere (which was characterized by very disturbed fields) and in the transition region between the outer and middle magnetospheres, there is no simple relationship between the density and field. Examples of anti-correlation, temperature or energy increases and dynamic processes are found. 相似文献
80.
J. Pamić K. Balogh H. Hrvatović D. Balen I. Jurković L. Palinkaš 《Mineralogy and Petrology》2004,82(1-2):65-79
Summary K–Ar and Ar–Ar whole rock and mineral ages are presented for 25 samples of metamorphic rocks from the Mid-Bosnian Schist Mts., representing one of the largest allochthonous Palaeozoic terranes incorporated within the Internal Dinarides. Four main age groups can be distinguished: 1) Variscan (343Ma), 2) post-Variscan (288–238Ma), 3) Early Cretaceous (mainly 121–92Ma), and 4) Eocene (59–35Ma) ages. Apart from this, an Oligocene (31Ma) age was obtained on Alpine vein hyalophane. The radiometric dating indicates a polyphase metamorphic evolution of the Palaeozoic formations and suggests a pre-Carboniferous age of the volcano-sedimentary protoliths, an Early Carboniferous age of Variscan metamorphism and deformation, post-Variscan volcanism, an Early Cretaceous metamorphic overprint related to out-of-sequence thrusting of the Palaeozoic complex, and an Eocene and Oligocene metamorphic overprint related to the main Alpine compressional deformation and subsequent strike-slip faulting, and uplift of the metamorphic core. Accordingly, the Mid-Bosnian Schist Mts. can be correlated in its multistage geodynamic evolution with some Palaeozoic tectonostratigraphic units from the Austroalpine domain in the Eastern Alps.Deceased 相似文献