Instability of interaction of interplanetary events with the earth's magnetosphere over long periods of time

Summary The position and size of the maximum of a model curve with one maximum during a half year were sought to provide the best linear relation between selected parameters, describing the geoactive event in the interplanetary medium, and the geomagnetic activity indices used and modulated additively by a model curve. The maxima for the separate half-years do not tend to cumulate and thus indicate that the sensitivity of the magnetosphere's reaction to an external stimulus may depend on parameters others than the angle of incidence at the magnetosphere.

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Резюме Искaлось месmоnоложенuе u знaченuе мaксuмумa мо?rt;ельноŭ крuвоŭ с о?rt;нuм мaкрuмумом в mеченuе nолу о?rt;a с целью nолучumь нauлучщее лuнеŭное оmнощенuе меж?rt;у выбрaннымu naрaмеmрaмu, оnuсывaющuмu еоaкmuвное собыmuе в межnлaнеmaрноŭ сре?rt;е, u меж?rt;у uн?rt;ексaмu еомa нumноŭ aкmuвносmu, uсnользовaннымu u мо?rt;улuровaннымu a?rt;?rt;umuвно nрu nомощu мо?rt;ельноŭ крuвоŭ. Мaксuмумы ?rt;ля оm?rt;ельных nолу о?rt;uŭ не nроявляюm mен?rt;енцuю к кумуляцuu u, maкuм обрaзом, свu?rt;еmельсmвуюm о mом, чmо чувсmрвumельносmь реaкцuu мa нumосферы к внещнему сmuмулу можеm зaвuсеmь оm ?rt;ру uх naрaмеmров, a не оm у лa na?rt;енuя нa мa нumосферу.

     

Approximative ray tracing and the accuracy of earthquake localization in media approximated by block structures

Summary Localization errors made by approximating a given medium by a homogeneous rectangular block model and due to the approximative solution of two-point ray tracing are estimated for four different structures. The separate influence of the individual characteristics of the medium is discussed. The iterative Geiger method supplemented by a generalized inversion of the damped least-squares and Marquardt algorithm is used for localizating five hypothetical hypocentres using 9 stations. Travel times in the original structures, used as input data for localization, are calculated using a special ray tracing system.

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am uu auauu a annuau a ¶rt; ¶rt; ma u ma ¶rt;¶rt; u annuau m a ¶rt; munau nuuum .

     

Simultaneous determination of Earth orientation parameters and station coordinates from combination of results of different observation techniques

Described is a method for non-regular combination of different techniques, where the normal equations matrix cannot be restored, to obtain a representative set of Earth orientation parameters and station coordinates. The method is based on combining station position vectors transformed to the celestial reference frame, where they are functions of both the EOP and the station coordinates. Three types of constraints are applied to stabilize the system, separate celestial pole offset from polar motion and, to tie the EOP between individual epochs. VLBI, GPS, SLR and Doris data as collected for the ‘IERS SINEX Combination Campaign’ was used to check the method. After combination, dispersion of station coordinates decreased from 0.040 to 0.031 m. The effect of the combination on EOP is of the order of 0.2 mas and it can be seen in Figs. 3 and 4 as a difference of the final and a priori values.     

A note on dynamic ray tracing in ray-centered coordinates in anisotropic inhomogeneous media

Dynamic ray tracing plays an important role in paraxial ray methods. In this paper, dynamic ray tracing systems for inhomogeneous anisotropic media, consisting of four linear ordinary differential equations of the first order along the reference ray, are studied. The main attention is devoted to systems expressed in a particularly simple choice of ray-centered coordinates, here referred to as the standard ray-centered coordinates, and in wavefront orthonormal coordinates. These two systems, known from the literature, were derived independently and were given in different forms. In this paper it is proved that both systems are fully equivalent. Consequently, the dynamic ray tracing system, consisting of four equations in wavefront orthonormal coordinates, can also be used if we work in ray-centered coordinates, and vice versa. vcerveny@seis.karlov.mff.cuni.cz     

Residual errors in altimetry data detected by combinations of single- and dual-satellite crossovers

 The single- and dual-satellite crossover (SSC and DSC) residuals between and among Geosat, TOPEX/Poseidon (T/P), and ERS 1 or 2 have been used for various purposes, applied in geodesy for gravity field accuracy assessments and determination as well as in oceanography. The theory is presented and various examples are given of certain combinations of SSC and DSC that test for residual altimetry data errors, mostly of non-gravitational origin, of the order of a few centimeters. There are four types of basic DSCs and 12 independent combinations of them in pairs which have been found useful in the present work. These are defined in terms of the `mean' and `variable' components of a satellite's geopotential orbit error from Rosborough's 1st-order analytical theory. The remaining small errors, after all altimeter data corrections are applied and the relative offset of coordinate frames between altimetry missions removed, are statistically evaluated by means of the Student distribution. The remaining signal of `non-gravitational' origin can in some cases be attributed to the main ocean currents which were not accounted for among the media or sea-surface corrections. In future, they may be resolved by a long-term global circulation model. Experience with two current models, neither of which are found either to cover the most critical missions (Geosat & TOPEX/Poseidon) or to have the accuracy and resolution necessary to account for the strongest anomalies found across them, is described. In other cases, the residual signal is due to errors in tides, altimeter delay corrections or El Ni?o. (Various examples of these are also presented.) Tests of the combinations of the JGM 3-based DSC residuals show that overall the long-term data now available are well suited for a gravity field inversion refining JGM 3 for low- and resonant-order geopotential harmonics whose signatures are clearly seen in the basic DSC and SSC sets. Received: 15 January 1999 / Accepted: 9 September 1999     

The Žermanice sill: new insights into the mineralogy,petrology, age,and origin of the teschenite association rocks in the Western Carpathians,Czech Republic

International Journal of Earth Sciences - The Žermanice locality represents the best-exposed example of the meta-basaltoid/meta-gabbroic rock type of the teschenite association. It forms a...     

Connectivity of the Coarsest Fraction in Headwater Channels: Imprints of Fluvial Processes and Debris‐Flow Activity

Some steep headwater streams of the mid‐mountains landscape of the flysch belt of the Western Carpathians are affected by debris flows. Connectivity of the largest boulder and cobble fractions has been evaluated in steep streams found in the transitional zones between the hillslopes and alluvial cones of similar lithology and watershed morphometry. Two longitudinal profiles affected by past debris‐flow activity and two longitudinal profiles void of such processes were selected. In the first case, active channels were characterised by the presence of the coarsest fraction, while a downstream trend of sediment coarsening or fining lacked any influence of contemporary fluvial processes and sediment supply. In addition, debris‐flow‐affected streams showed greater differences between the middle axis of the coarsest particle and the particle‐size index including the lengths of all three axes, which is most likely the result of limited active fluvial transport. All the studied streams demonstrated general downstream fining of the largest particles, which resulted from local flysch lithology containing more resistant sandstones in the upper parts of the watershed. The trend of sediment fining was more rapid in the longitudinal profiles unaffected by past debris flows. These types of streams also showed adjustment of the coarsest bed fraction to contemporary processes in channels by sediment coarsening in incised reaches and sediment fining in depositional reaches as well as by downstream response to some lateral sediment inputs. The index of the unit stream power showed no correlation with the considered coarsest fraction in both fluvial‐dominated channels and debris‐flow‐affected channels.     

Fresnel volumes corresponding to PKP waves in the IASP91 model

Fresnel volumes provide a suitable tool for estimating the resolution limits or accuracy of tomographic methods based only on the arrival times of these seismic waves, which penetrate the deep interior of the Earth. The standard definition of the Fresnel volume was modified to include effects of multipathing, i.e., multivalued travel times. Computations were performed in the IASP91 model for three representative epicentral distances and two prevailing signal periods. Preliminary results have been obtained. They place a rather strong restriction on the resolution limits of tomographic methods, depending on the prevailing period, due to the relatively large fatness of PKP Fresnel volumes.     

广州市不同类型水体轮虫群落结构的时空变动及与理化因子间的关系

轮虫是水体中重要的浮游生物类群,对环境变化敏感,是水生态系统中食物链及微型食物网的关键环节.于2015年夏季(7月)和冬季(12月)对养殖池塘、水库、广州城市湖泊、珠江河口及珠江河段水域的轮虫和理化环境指标进行了调查分析,共发现轮虫26属、76种,其中裂痕龟纹轮虫(Anuraeopsis fissa)在7月河流水体占绝对优势,但12月数量明显减少.冬季珠江河段和河口水体群落多样性指数与均匀度指数较夏季高,群落结构较夏季稳定.调查水体轮虫丰度范围为33~2625 ind./L,城市湖泊夏季丰度较高,冬季有所下降,而养殖池塘轮虫丰度在冬季有所上升.群落结构相似性分析(ANOSIM)分析表明,不同类型水体之间差异显著,尤以湖泊与河流差异性最大,广布多肢轮虫(Polyarthra vulgaris)在湖泊贡献率最高,暗小异尾轮虫(Trichocerca pusilla)其次;裂痕龟纹轮虫在河流贡献率最高,优势种丰度差异是造成湖泊与河流群落结构差异的主要原因.统计分析表明,轮虫丰度与叶绿素a浓度呈正相关.冗余分析与ANOSIM分析发现广布多肢轮虫在流花湖等叶绿素a浓度较高的静态水体中易形成优势;裂痕龟纹轮虫和角突臂尾轮虫(Brachionus angularis)在珠江河段等总氮和总磷浓度高的富营养化流动水体中易形成优势.综合轮虫群落结构和水质特征,广州市水体富营养化严重,耐污性轮虫种类多,应加强城市水生态系统保护和管理.     

Reactive monazite and robust zircon growth in diatexites and leucogranites from a hot,slowly cooled orogen: implications for the Palaeoproterozoic tectonic evolution of the central Fennoscandian Shield,Sweden

Monazite in melt-producing, poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages during orogenic evolution particularly in hot, slowly cooling orogens such as the Svecofennian. Owing to the high heat flow in such orogens, small variations in pressure, temperature or deformation intensity may promote a mineral reaction. Monazite in diatexites and leucogranites from two Svecofennian domains yields older, coeval and younger U–Pb SIMS and EMP ages than zircon from the same rock. As zircon precipitated during the melt-bearing stage, its U–Pb ages reflect the timing of peak metamorphism, which is associated with partial melting and leucogranite formation. In one of the domains, the Granite and Diatexite Belt, zircon ages range between 1.87 and 1.86 Ga, whereas monazite yields two distinct double peaks at 1.87–1.86 and 1.82–1.80 Ga. The younger double peak is related to monazite growth or reprecipitation during subsolidus conditions associated with deformation along late-orogenic shear zones. Magmatic monazite in leucogranite records systematic variations in composition and age during growth that can be directly linked to Th/U ratios and preferential growth sites of zircon, reflecting the transition from melt to melt crystallisation of the magma. In the adjacent Ljusdal Domain, peak metamorphism in amphibolite facies occurred at 1.83–1.82 Ga as given by both zircon and monazite chronology. Pre-partial melting, 1.85 Ga contact metamorphic monazite is preserved, in spite of the high-grade overprint. By combining structural analysis, petrography and monazite and zircon geochronology, a metamorphic terrane boundary has been identified. It is concluded that the boundary formed by crustal shortening accommodated by major thrusting.