Large density fluctuations in the martian ionosphere as observed by the Mars Express radar sounder     

D.A. Gurnett  D.D. Morgan  F. Akalin  R.A. Frahm  S. Barabash 《Icarus》2010,206(1):83-94

The MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on the Mars Express spacecraft provides both local and remote measurements of electron densities and measurements of magnetic fields in the martian ionosphere. The density measurements show a persistent level of large fluctuations, sometimes as much as a factor of three or more at high altitudes. Large magnetic field fluctuations are also observed in the same region. The power spectrums of both the density and magnetic field fluctuations have slopes on a log-log plot that are consistent with the Kolmogorov spectrum for isotropic fluid turbulence. The fractional density fluctuation, Δn_e/n_e, of the turbulence increases with altitude, and reaches saturation, Δn_e/n_e ∼ 1, at an altitude of about 400 km, near the nominal boundary between the ionosphere and the magnetosheath. The fluctuations are usually so large that a well-defined ionopause-like boundary between the ionosphere and the solar wind is seldom observed. Of mechanisms that could be generating this turbulence, we believe that the most likely are (1) solar wind pressure perturbations, (2) an instability in the magnetosheath plasma, such as the mirror-mode instability, or (3) the Kelvin-Helmholtz instability driven by velocity shear between the rapidly flowing magnetosheath and the ionosphere.  相似文献   

An Andean type Palaeozoic convergence in the Bohemian Massif     

Karel Schulmann  Jiří Konopásek  Vojtĕch Janoušek  Ondrej Lexa  Jean-Marc Lardeaux  Jean-Bernard Edel  Pavla Štípská  Stanislav Ulrich 《Comptes Rendus Geoscience》2009,341(2-3):266-286

The geological inventory of the Variscan Bohemian Massif can be summarized as a result of Early Devonian subduction of the Saxothuringian ocean of unknown size underneath the eastern continental plate represented by the present-day Teplá-Barrandian and Moldanubian domains. During mid-Devonian, the Saxothuringian passive margin sequences and relics of Ordovician oceanic crust have been obducted over the Saxothuringian basement in conjunction with extrusion of the Teplá-Barrandian middle crust along the so-called Teplá suture zone. This event was connected with the development of the magmatic arc further east, together with a fore-arc basin on the Teplá-Barrandian crust. The back-arc region – the future Moldanubian zone – was affected by lithospheric thinning which marginally affected also the eastern Brunia continental crust. The subduction stage was followed by a collisional event caused by the arrival of the Saxothuringian continental crust that was associated with crustal thickening and the development of the orogenic root system in the magmatic arc and back-arc region of the orogen. The thickening was associated with depression of the Moho and the flux of the Saxothuringian felsic crust into the root area. Originally subhorizontal anisotropy in the root zone was subsequently folded by crustal-scale cusp folds in front of the Brunia backstop. During the Visean, the Brunia continent indented the thickened crustal root, resulting in the root's massive shortening causing vertical extrusion of the orogenic lower crust, which changed to a horizontal viscous channel flow of extruded lower crustal material in the mid- to supra-crustal levels. Hot orogenic lower crustal rocks were extruded: (1) in a narrow channel parallel to the former Teplá suture surface; (2) in the central part of the root zone in the form of large scale antiformal structure; and (3) in form of hot fold nappe over the Brunia promontory, where it produced Barrovian metamorphism and subsequent imbrications of its upper part. The extruded deeper parts of the orogenic root reached the surface, which soon thereafter resulted in the sedimentation of lower-crustal rocks pebbles in the thick foreland Culm basin on the stable part of the Brunia continent. Finally, during the Westfalian, the foreland Culm wedge was involved into imbricated nappe stack together with basement and orogenic channel flow nappes.  相似文献   

Temperature properties of gravity meter Gs 15 No. 228     

Zdeněk Šimon  Stanislav Holub  Reviewer J. Pícha 《Studia Geophysica et Geodaetica》1981,25(2):107-123

uu mnam a anu nuuauma Gs 15 No 228 u a m mnam m nua a n u — . (5). au u n¶rt; a 5 u a ¶rt;mu annaam n aa uu mnam — a. 1. ¶rt;: uum mmamuauauma (1/191), mamuu mnam uum annaam (–5,24 ^–2/°C), mamuu mnam uum uum umauma (–1 ^–2/°C). m u anum¶rt; u a amm aamumuu u uu — a. 2, 3 u u. 6, 7. aua uu auau mnam a anuauma nu nu¶rt; 6 a — a n¶rt; mamu mnam uu.  相似文献   

Remarks on the mechanism of surface-pressure changes in baroclinic atmosphere     

Stanislav Brandejs 《Studia Geophysica et Geodaetica》1957,1(2):387-390

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Application of the restrictedD-optimal design to gravimetry     

Ludmila Kubáčková  Ivana Jakubcová  Miloš Pick  Stanislav Hrách  Reviewer J. Anděl  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1979,23(1):10-16

Summary The theory of the restricted D-optimal design was used for the project of gravity measurements in a pressure chamber. An example of the measurements is presented.  相似文献   

A model of Meridional energy transport     

Stanislav Brandejs  Reviewer F. Pechala 《Studia Geophysica et Geodaetica》1976,20(3):284-294

Summary A number of relations describing various forms of energy transport in the atmosphere have been derived and several simplification, unsuitable according to the author's opinion, which are introduced in applying them, are pointed out.  相似文献   

The 60th birthday of Dr. František Link     

Stanislav Brandejs 《Studia Geophysica et Geodaetica》1967,11(1):110-110

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First results from the plasma composition spectrometer PROMICS-3 in the Interball project     

I. Sandahl  S. Barabash  H. Borg  E. Yu. Budnik  E. M. Dubinin  U. Eklund  H. Johansson  H. Koskinen  K. Lundin  R. Lundin  A. Mostrom  R. Pellinen  N. F. Pissarenko  T. Pulkkinen  P. Toivanen  A. V. Zakharov 《Annales Geophysicae》1997,15(5):542-552

PROMICS-3 is a plasma experiment flown in the Russian project Interball. It performs three-dimensional (3D) measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 12 eV–35 keV. The Interball project consists of two main satellites, the Tail Probe and the Auroral Probe, each with one subsatellite. The Interball Tail Probe was launched on 3 August 1995, into a 65° inclination orbit with apogee at about 30 R_E. Both main satellites carry identical PROMICS-3 instruments and thus direct comparisons of the particle distributions will be possible once the Auroral Probe is launched. Furthermore, PROMICS-3-Tail is the first instrument measuring the 3D ion distribution function in the magnetospheric boundary layers at high latitudes. In this paper we describe the PROMICS-3 instrument and show initial results from the Tail probe, measurements of the mag-netosheath, plasma sheet, and ring current plasmas.  相似文献   

Interaction of powered supports and the strata in coal seams under a heavy roof     

Budirský  Stanislav 《Geotechnical and Geological Engineering》1985,3(2):113-138

Summary The interaction of powered supports and the strata in thick coal seams under a heavy roof is discussed when subjected to anomalous phenomena, particularly rock bursts, which have occurred in the Upper Silesian Coal Basin in the last few years. On the basis of the results of long-term field measurements and theoretical analyses, the necessary setting and yield loads of powered supports as well as loading patterns which appear during rock bursts have been determined. A methodology for the testing of powered supports destined for coal seams prone to rock bursts, for the implementation of which a rapid closure rig should be built, is proposed.  相似文献   

Microstructure mechanism map of dynamically recrystallized marble     

Stanislav Ulrich  Alan B. Thompson  Karel Schulmann  Martin Casey   《Tectonophysics》2006,412(3-4):173-182

The relative nucleus density (RND) model of dynamically recrystallized grain size [Sakai, T., Jonas, J.J. 1984. Dynamic recrystallization: mechanical and microctructutal consideration. Acta metallurgica, 32, 198–209] was applied to experimentally and to naturally deformed marbles that have undergone dynamic recrystallization. The model shows that a relationship between initial grain size (D₀) and stable dynamically recrystallized grain size (D_S) for a given value of temperature-corrected strain-rate (Z) controls grain size evolution during dynamic recrystallization. New microstructural mechanism maps (MM-maps) for experimentally and naturally deformed marbles (based on previously published data) were defined in log grain size–log Z space and show two distinct regions of grain reduction and grain coarsening. The boundary between these two regions corresponds to an equation relating dynamically recrystallized grain size and temperature corrected strain rate, as proposed in this work. The new MM-map was used to trace semi-quantitatively microstructural and grain size evolution in naturally deformed marbles that underwent dynamic recrystallization at different thermal conditions. The boundary between grain coarsening and grain reduction does not necessarily coincide with the boundary between rotation and migration recrystallization mechanisms. Assessment of available natural data shows that the boundary condition D₀ = 2D_S between grain-coarsening and grain-reduction introduced by Sakai and Jonas [Sakai, T., Jonas, J.J. 1984. Dynamic recrystallization: mechanical and microctructutal consideration. Acta metallurgica, 32, 198–209] is not required for naturally deformed marble.  相似文献