北京大灰厂试验场重力变化特征及其解释

介绍了北京大灰厂试验场（简称京西试验场）的概况，对１９９３年３月以来重力重复观测资料进行了处理。计算了各期重力观测精度，结果显示１９９３年３月～１９９５年５月京西试验场存在一定重力变化。采用给定的模型反演了八宝山断层介质的密度变化，认为断层破碎带介质密度的变化可能是引起地表重力变化的主要因素     

Geopotential from space techniques

The monitoring of the perturbed motion of artificial satellites since the 1960's has provided a valuable resource for improved activities in geodesy. These observations and the improved geodetic techniques they fostered have provided an unparalleled means for studying both the gravity field and the Earth's shape. In this paper, we will review the various determinations of the Earth's gravity field produced at many research centers over the years from space techniques. The specific methods which have been used to measure our planet, such as satellite altimetry and satellite orbital perturbation analyses (over short and long periods of time), will be compared.     

用区域重力资料确定的华北地台南缘地缝合线及其地质意义

利用１∶２０万区域重力资料，结合航磁，电磁测深、遥感、天然地震等丰富的地质、地球物理资料，根据断裂的地质、地球物理标志，在华北地台南缘发现并确定了控制火山喷发的裂隙—中心式古火山通道，即隐伏的北西西向的上戈—铁炉坪—付店超壳断裂带。该断裂属华北地台南缘不同时代、不同性质的近东西向的地缝合线。研究认为：该断裂及其次级断裂不仅是重要的长期多次活动的控岩、导矿和容矿构造，而且也为矿床的多次改造、叠加和再富集提供了热源。它的发现，对重新认识豫西地区大地构造的演化特征，建立新的成矿模式，拓宽该区的找矿前景具有重要意义。     

Energy of a Stringy Charged Black Hole in the Teleparallel Gravity

We use the teleparallel geometry analog of the Møller energy-momentum complex to calculate the energy distribution (due to matter plus field including gravity) of a charged black hole solution in heterotic string theory. We find the same energy distribution as obtained by Gad who investigated the same problem by using the Møller energy-momentum complex in general relativity. The total energy depends on the black hole mass M and charge Q. The energy obtained is also independent of the teleparallel dimensionless coupling constant, which means that it is valid not only in the teleparallel equivalent of general relativity, but also in any teleparallel model. Furthermore, our results also sustains (a) the importance of the energy-momentum definitions in the evaluation of the energy distribution of a given spacetime and (b) the viewpoint of Lessner that the Møller energy-momentum complex is a powerful concept of energy and momentum.     

Nature of the iogenic plasma source in Jupiter's magnetosphere: II. Near-Io distribution

Three-dimensional calculations are presented for the distribution of the iogenic plasma source that is created near Io (i.e., within ∼24 satellite radii about Io) by O and S gases located in the volume above Io's exobase (i.e., corona and escaping extended neutral clouds, designated as the “Outer Region”) and are complementary to a preceding paper for calculations on a circumplanetary scale. The instantaneous pickup ion production rates for both electron impact and charge exchange have significant radial, north-south, and orbital-plane asymmetries beginning just inside and/or beyond Io's Lagrange sphere (5.81 Io radii) and, within the Lagrange sphere, are distributed nearly symmetrically about Io and are highly peaked about Io's exobase. The spatial natures of the corresponding pickup ion density, mass loading rates, and the pickup ion conductivity, current, and magnetic field are investigated. Spatially integrated rates are calculated for the corona volume and compared to larger Outer Region circumplanetary volumes and are also compared to estimates drawn from the scientific literature (but not modeled here) of the spatially integrated rates for pickup processes in the strongly perturbed “Inner Region” below the exobase. Within the corona volume, the spatially-integrated net-mass loading rate and total (electron impact and charge exchange) mass loading rate are only a factor of ∼3 and ∼5, respectively, smaller than those estimated for the Inner Region, whereas for the whole plasma torus, the Outer Region rates are larger or comparable to those estimated for the Inner Region. The total pickup ion gyration power supplied to the whole plasma torus is estimated to be significantly less than the power radiated by the plasma torus, indicating that an additional power source, likely a circumplanetary distribution of nonthermal electrons, is present.     

Synchrotron radiation from the Crab Nebula discriminates between models of space–time foam

It has been argued by Jacobson, Liberati and Mattingly that synchrotron radiation from the Crab Nebula imposes a stringent constraint on any modification of the dispersion relations of the electron that might be induced by quantum gravity. We supplement their analysis by deriving the spectrum of synchrotron radiation from the coupling of an electrically charged particle to an external magnetic fields in the presence of quantum-gravity effects of the general form (E/M_QG). We find that the synchrotron constraint from the Crab Nebula practically excludes 1.74 for M_QGm_P=1.2×10¹⁹ GeV. On the other hand, this analysis does not constrain any modification of the dispersion relation of the photon that might be induced by quantum gravity. We point out that such quantum-gravity effects need not obey the equivalence principle, a point exemplified by the Liouville-string D-particle model of space–time foam. This model suggests a linear modification of the dispersion relation for the photon, but not for the electron, and hence is compatible with known constraints from the Crab Nebula and elsewhere.     

Near-infrared spectral monitoring of Triton with IRTF/SpeX I: establishing a baseline for rotational variability

We present eight new 0.8 to 2.4 μm spectral observations of Neptune's satellite Triton, obtained at IRTF/SpeX during 2002 July 15-22 UT. Our objective was to determine how Triton's near-infrared spectrum varies as Triton rotates, and to establish an accurate baseline for comparison with past and future observations. The most striking spectral change detected was in Triton's nitrogen ice absorption band at 2.15 μm; its strength varies by about a factor of two as Triton rotates. Maximum N₂ absorption approximately coincides with Triton's Neptune-facing hemisphere, which is also the longitude where the polar cap extends nearest Triton's equator. More subtle rotational variations are reported for Triton's CH₄ and H₂O ice absorption bands. Unlike the other ices, Triton's CO₂ ice absorption bands remain nearly constant as Triton rotates. Triton's H₂O ice is shown to be crystalline, rather than amorphous. Triton's N₂ ice is confirmed to be the warmer, hexagonal, β N₂ phase, and its CH₄ is confirmed to be highly diluted in N₂ ice.     

Relative contributions of sublimation and volcanoes to Io's atmosphere inferred from its plasma interaction during solar eclipse

We present a model that describes Io's delayed electrodynamic response to a temporal change in Io's atmosphere. Our model incorporates the relevant physical processes involved in Io's atmosphere-ionosphere-magnetosphere electrodynamic interaction to predict the far-ultraviolet (FUV) radiation as Io enters Jupiter's shadow and re-emerges into sunlight. The predicted FUV brightnesses are highly nonlinear as the strength of the electrodynamic interaction depends on the ratios of ionospheric conductances to the torus Alfvén conductance, but the former are functions of electrodynamics and the atmospheric density, which decays rapidly upon entering eclipse. Key factors governing the time evolution are the column density due to sublimation and the column density due to volcanoes, which maintain the background atmosphere during eclipse. The plasma interaction does not react instantaneously, but lags to a temporarily changing atmosphere. We find three qualitatively different scenarios with two of them including a post-eclipse brightening. The brightness ratio of in-sunlight/in-eclipse coupled with the existence of a sub-jovian equatorial spot constrains the volcanic column density to several times 10¹⁸ m⁻², based on the currently available observations. Thus in sunlight, the sublimation driven part of Io's atmosphere dominates the volcanically driven contribution by roughly a factor of 10 or more.     

月球重力场对绕月低轨卫星的长期影响

从解析形式出发,利用月球重力场模型JGL165P1,分析了月球重力场(带谐项)对绕月低轨卫星的长期影响。为了减少计算误差,保证计算精度,在分析解中使用循环公式来计算倾角函数。结果指出对于一个高度为100km的极月轨道卫星,冻结轨道存在的可能性不大,但是当轨道倾角在i=90°附近或者高度再高一些,则有可能存在冻结轨道;对于100km高的初始圆轨道,卫星在无控的情况下半年内将会坠落到月球表面,如果高度增加到200km,则不进行轨道控制也不会坠落到月面上。利用仿真软件GEODYN解算出来的结果证实了上述结论。     

洱海近区非潮汐重力变化的研究

本文给出了洱海水体变化对局部重力场影响的解析式和量级,并且将理论结果与实测的水文、流动重力及定点重力分析结果作了比较,结果表明:影响的程度因距洱海的距离而异。在台站重力测量中,由水体变化产生的干扰淹没在零漂之中(约占每日零漂量的2％),潮汐主频段上没有明显的干扰信号;而对流动重力测量,在水体变化大的情况下,部分测点所产生的变化可以达到10×10~(-8)m/s~2。