Large-scale structure of magnetospheric plasma

Recent investigations of magnetospheric plasma structure are summarized under the broad categories of empirical models, transport across boundaries, formation, and dynamics of the plasma sheet. This report reviews work in these areas during the period 1991 to 1993. Fully three-dimensional empirical models and simulations have become important contributors to our understanding of the magnetospheric system. Some new structural concepts have appeared in the literature: the entry boundary and geopause, the plasma sheet region 1 vortices, the low-energy layer, the adiabaticity boundary or wall region, and a region in the tail to which we refer as the injection port. Traditional structural concepts have also been the subject of recent study, notably the plasmapause, the magnetopause, and the plasma sheet. Significant progress has been made in understanding the nature of plasma sheet formation and dynamics, but the acceleration of electrons to high energy remains somewhat mysterious.     

The joint influence of the Coriolis force and the stratification on stationary motions in the zonal model of equatorial atmosphere

Summary In the framework of a zonal model of the equatorial atmosphere, the joint influence of the Coriolis force and stratification on stationary motion is studied. In addition we assume a Boussinesq approximation and consider the equatorial region as a macrodisturbance localized round the Equator, against a background of an isothermal atmosphere with a zonal distribution. Exact analytical solutions of the system of equations (1)–(5) are obtained and analyzed. An interesting result is that the equatorial atmosphere could exist in different stationary states in each of them separately, as well as in a number of them simultaneously.     

Results of concentration and mobility measurements of positively and negatively charged particles taken by a rocket-borne parachuted aspiration (Gerdien) probe in the height region from 72 to 39 km

Summary With a self-neutralizing, rocket-borne parachute aspiration probe concentration and mobility measurements of positively and negatively charged carriers were made between 72 and 40 km over Sardinia. Between 72 km and 60 km a heavy and a light group of positively charged particles were found. The heavy group was more abundant than the hight group in the greater heights. For the negatively charged particles only one mobility group was found which roughly corresponded to the mobility of the light group of the positively charged carriers. The probe was designed so that no electrons could enter the analyzer section of the aspiration system. By this the electron concentration was given by the difference in concentration between the positively and negatively charged particles.This paper was read byH. Dolezalek, in an abbreviated form supplied by the authors.     

Numerical modeling of the high-latitude F-layer anomalies

The results of a detailed numerical study of the behaviour of the convective polar ionosphere are presented. The developed theoretical model produces three-dimensional distribution of electron density, electron and ion temperature. The effects of auroral particle precipitation on the density and temperature structures are studied for winter and low solar activity conditions. The high-latitude ionospheric features, such as the tongue of ionization, the main trough the polar ionization peak, the auroral ionization peak, the high-latitude ionization hole, the tongue of electron temperature, the high latitude minima of electron, temperature, and the ion temperature hot spot are obtained from calculations.Numerically obtained results are used for determining the HF propagation paths in the polar ionosphere. The effects of ionospheric irregularities on high frequency ionospheric radio waves are investigated by using a three-dimensional ray-tracing computer program. Ray-path trajectories are presented for different values of the elevation angle of transmission. From our study, it was found that large-scale irregularity structures of the high-latitude ionosphere, in the presence of the earth's magnetic field, significantly affect high frequency radio wave propagation.     

Generators in atmospheric electricity

Summary The definition of a generator in atmospheric electricity is considered, and various phenomena are discussed as to whether they can be described as generators.     

Calculation of particle distribution by the data on spectral transparency

, , . . , , , . , , .Summary A general method for obtain the particle size distribution curve of the dispersed system is developed according to data of its spectral transparency, based onMellin's transformation. The method does not contain any arbitrary suppositions about spectrum character of particles. A simple calculation scheme is supposed, examples of inversion are given, the range of spectrum and the accuracy of transparency measurements necessary to obtain the inversion with a given accuracy are estimated. The calculation scheme is appropriate for every kind of errors of measurement and calculation and contains moderate requirements to their accuracy.     

A note on the general concept of wave breaking for Rossby and gravity waves

A recently proposed general definition of wave breaking is further discussed, in order to deal with some points on which misunderstanding appears to have arisen. As with surface and internal gravity waves, the classification of Rossby waves into breaking and not breaking is a generic classification based on dynamical considerations, and not a statement about any unique signature or automatically recognizable shape. Nor is it a statement about passive tracers uncorrelated with potential vorticity on isentropic surfaces. A strong motivation for the definition is that proofs of the nonacceleration theorem of wave, mean-flow interaction theory rely, explicitly or implicitly, on a hypothesis that the waves do not break in the sense envisaged.The general definition refers to the qualitative behaviour of a certain set of material contours, namely those, and only those, which would undulate reversibly, with small slopes, under the influence of the waves' restoring mechanism, in those circumstances for which linearized, nondissipative wave theory is a self-consistent approximation to nonlinear reality. The waves' restoring mechanism depends upon the basic-state vertical potential density gradient in the case of gravity waves, and upon the basic-state isentropic gradient of potential vorticity in the case of Rossby waves. In the usual linearized theory of planetary scale Rossby waves on a zonal shear flow, the relevant material contours lie along latitude circles when undisturbed.     

Sunspot indices characterizing the 11-year cycle as a whole and their relationship to the analogous indices of geomagnetic activity

Summary Sunspot indices characterizing the 11-year cycle as a whole were determined on the basis of Wolf's sunspot numbers and their total area as well as on the basis of the primary physically indices of the spot-generating activity of the Sun.Their interrelationship is shown and their relationship to the indices of geomagnetic activity aa and C_i is examined. It is shown that under high solar activity a certain saturation of the Earth's magnetosphere occurs and that the variations of geomagnetic activity correlate with the variations of the global sunspot indices (Wolf number and total area) but correlate but slightly with the primary physically sunspot indices.

---

u u n¶rt;;u nm u uuu nu u¶rt;; nmaoam ¶rt;;mmu q, n¶rt;; u¶rt;;u nm, aamuu -mu u . aaa u aua u u u mu u¶rt;;a ¶rt;;a¶rt;;um amumu aa u _i. aa, m nu amumu mynam am aum u m auauu ¶rt;;a¶rt;;umo amumu um auauau ¶rt;; u¶rt;; nm (u a, aa na¶rt;), a um uuu nuu u¶rt;u nm.

     

Seismotectonic and refraction seismic investigations in the border region between the Eastern Alps and the Pannonian Basin

Focal solutions of four strong earthquakes and P signals of twenty-four smaller shocks of the active Mur-Mürz Valley, the Semmering Pass and the Vienna Basin. An equivalent slip rate of 0.03 This feature agrees with the model of a subsiding Pannonian Basin. An equivalent slip rate of 0.03 cm/year is roughly estimated from earthquake data 1903–1978. This rate does not include the creep rate, but it gives an idea of the magnitude of speed of geological processes in this area.Refraction seismic data from the Alpine Longitudinal Profile 75 shows a low velocity zone in the upper crust of the seismic active East Alpine area but not in the aseismic part of the Pannonian Basin.The eastern margin of the Eastern Alps and the Carpathians limits the Pannonian Basin, which has a special and interesting geological history. Many authors (Szadezky-Kardoss, 1966;Stegena, Ceszy andHorvàth, 1975) presented models of the genesis of the Pannonian Basin. They apply the concept of the mantle diapirs to explain the following facts:subsiding of the Pannonian Plate in comparison to the Alps, high terrestrial heat flow within the Pannonian Plate, decrease of the Moho depth from 40 km below the Eastern border of the Alps to 27 km below the Pannonian Basin. They claim that the Alpine-Carpathian interarc and basin represent the final stage of an orogenetic system where subcrustal erosion leads to a thinning of the crust. Consequently the surface subsides and is covered by young sediments. They proved that this subsidence and sedimentation is more or less in isostatic equilibrium. The aim of this paper is to provide new arguments using focal solutions and refraction seismic investigations.     

Long-period fluctuations observed in the ionospheric absorption variations

Summary By subsequent application of power spectrum analysis, autocorrelation analysis and fast Fourier transform (FFT) of the day- and night-time absorption values of five LF radio-paths (164 kHz, 155 kHz, 185 kHz, 218 kHz and 272 kHz) in Europe during the interval 1 June 1979–30 June 1980, fluctuations with the following basic (fundamental), commonly recurrent periods were found: 3.5–5 days and 10.5–12 days. They exist in all investigated time series, while 6- and 9-day fluctuations are observed on the northern radio-paths (185 kHz and 272 kHz). Shorterperiod oscillations are most active during autumn and especially during winter, while the longerperiod oscillation (10.5–12-day) has significant amplitudes also in summer.

---

n n¶rt;am nuu aaua nma mu, amu aaua u m maauu () ¶rt; u ¶rt;a n nu u nmu a¶rt;u ma (164 , 155 , 185 , 218 u 272 ) a¶rt; n nu¶rt; 1 u 1979–30 u 1980. u a¶rt; ¶rt;u (¶rt;ama) nmu nu¶rt;: 3.5–5 ¶rt; u 10.5–12 ¶rt. u nummm u¶rt;a ¶rt;a. 6- u 9-m au a¶rt;am m a¶rt;umaa (185 u 272 ). ama au a amu u u u. ¶rt;nu¶rt; (10.5–12 ¶rt;) um aum anum¶rt; u m.

     

The gross features of the lithosphere-asthenosphere system in Europe from seismic surface waves and body waves

Long-period recordings of dispersive Rayleigh waves along numerous station lines, or profiles, in Europe have for the first time permitted a uniform inversion of these observations based on a new method of phase velocity regionalization.Regional dispersion relations obtained by this method have then been subjected to a complete inversion procedure commonly known as the hedgehog method. The results are presented in a map outlining the thickness of the lower lithosphere (lid) and the shear (S) velocities in both the lid and the asthenosphere channel.A comparison of these results with the minimum compressional (P) wave velocities in the asthenosphere and their corresponding depths provides an estimate of theV _p /V _s ratio for the asthenosphere in the European area.Contribution No. 314, Institute of Geophysics, ETH-Zürich, Switzerland.     

Least squares inversion of one-dimensional magnetotelluric data: An assessment of procedures employed by Brown University

The pirmary objective of this paper is to review inversion algorithms employed to interpret magnetotelluric data by the geophysical/electromagnetics group at Brown University. Examples are presented from a variety of tectonic regimes — the Rio Grande rift, the Colorado Plateau, and Iceland. Following a brief tutorial in which the basic relations for the inverse prrolem are developed, we discuss the detectability and resolvability of various elements of the models. The correlation between certain model parameters is stressed, a phenomena well-known to interpreters. In this paper we emphasize the importance of identifying the precise range of values for which two or more parameters are coupled — these ranges are defined by what wer term saturation limits. Generalized inverse theory is employed to arrive at optimal models which are evaluated in terms of resolution and information matrices. The degree to which models fit a given dat base can be assessed using several quantitative approaches. We have found that it is impotant not only to determine the best fitting model, but also to identify those marginal solutions which also fall within the range of uncertainty of the data. The results from our direct invverse method agree favorably with those from Monte Carlo methods.     

To three aniversaries of czechoslovak geophysics in 1983

Summary 30 years from the foundation of the Czechoslovak and Slovak Academy of Sciences in 1953 are commemorated in connection with 40 years elapsed from the decase of Prof. V. Láska, founder of gephysics in Cezchoslovakia. The progress achieved in its main lines and the outlooks of further development are described.

---

mam na 30-m u a u a aa¶rt;u a, ¶rt;a 1953-¶rt;, u u 40-mu m mu a . aa, amuuu auu. nua m mam u¶rt;au n anau u ¶rt;am nnmu ¶rt;a aumu.

     

Remarks on seismic energy release related to strike slip and tensile crack mechanisms

¶rt;u u uu uuu ¶rt; n¶rt; ¶rt;au m ¶rt;u uu m n¶rt;uu u numuu m¶rt;. mam n¶rt; aamumuu anamu u ; n¶rt; mu aaa amu ¶rt;u n¶rt;uu nmu aua ¶rt;u u uu a mu m muna.     

Review of Ray Theory Applications in Modelling and Imaging of Seismic Data

Throughout the last twenty years, 3D seismic ray modelling has developed from a research tool to a more operational tool that has gained growing interest in the petroleum industry. Various areas of application have been established and new ones are under development. Many of these applications require a modelling system with flexible, robust and efficient modelling algorithms in the core. The present paper reviews the basic elements of such a system, based on the open model concept and the wavefront construction technique. In the latter, ervený's dynamic ray tracing is an intrinsic part. The modelling system can be used for generating ray attributes and synthetic seismograms for realistic 3D surveys with tens of thousands of shots and receivers. Moreover, some other types of application areas are illustrated: Production of Green's functions for prestack depth migration and hybrid modelling (combined ray and finite-difference modelling), attribute mapping and illumination analysis, both for survey planning and interpretation. Finally, the concepts of isochron rays and velocity rays related to seismic isochrons have been introduced recently, with very interesting future applications.     

The connection between characteristic values of the 11-year cycles of solar and of geomagnetic activity

Summary Using the annual values of the indices of solar and geomagnetic activity for the period 1868–1976, the basic values characterizing the cycle as a whole were determined for the 11-year cycles nos 11–20, (Tab. 1). High values of the coefficients of correlation were found for some pairs of characteristic values of the same and different kinds, given in Tab. 2, which can be utilized for long-term predictions of geomagnetic activity.

---

a auu¶rt;u au u¶rt; uaum amumu muu 1868–1976 n¶rt; ¶rt; 11-mu u 11–20 naam aamuu u a (a. 1). u au uuma uu ¶rt; m na naam ¶rt;ua u ¶rt;ua ¶rt;a (a. 2), m m amu nuu nu ¶rt; nuauuaum amumu.

     

Seismic signals in geothermal areas of active volcanism: a case study from ‘La Fossa’, Vulcano (Italy)

Since the last eruption (1888–1890) volcanism at Vulcano, Aeolian Archipelago, southern Tyrrhenian Sea, has taken the form of persistent fumarolic activity. The gas-vapour phases of the geothermal systems are mainly discharged within two restricted areas about 1 km apart from each other, in the northern part of the island. These areas are La Fossa crater, and the beach fumaroles of the Baia di Levante. Fluids released at the two main fumarolic fields display quite different chemical and temperature characteristics, implying different origins. The local seismicity essentially takes the form of discrete shocks of shallow origin (depth1 km) at La Fossa, usually with energy < 10¹³ ergs. They are thought to be related to the uprise of pressurized hot gases and vapours discharged at the crater fumaroles. The present investigation points to the existence of two principal categories of seismic events (called M-shocks and N-shocks). These are short events (normally < 10 s). M-type shocks are thought to be due to resonance vibrations within the interior of the volcano, probably driven by the excitation of shock-waves within cavities deeply affected by deposition and alteration of self-sealant hydrothermal minerals. N-type events display features that resemble those of volcano-tectonic earthquakes, but have no recognizable S-phases. Here they are tentatively attributed to microfracturing of rocks which have been extensively hydrothermally altered. Results of the present study permit a preliminary conceptual model of the local shallow seismic processes in the framework of geochemical modelling of fumarolic activity and geological inferences from geothermal drilling.     

On free nutation of the rotation vector of a rigid body

aam, m ¶rt;-mau ¶rt;uu a ma au am m¶rt; ma m unmuu m m. ¶rt;a, u a u unmuu annuuam, m am n una u 0,1 u a u ammuuu ¶rt;mau aa m m.     

Nuclear technique in tracing the cumuli clouds

Summary Within the scopes of Mount Olympus Cumulus Project (sponsored by NATO) which is currently in progress on the summit of Mount Olympus (Hellas), a new method has been applied, with non radioactive tracers, which would become radioactive afterwards by neutron irradiation at the Democritus (Athens) nuclear reactor.To this effect the solution of the tracers (various chemical compounds) was injected into the cumuli clouds by spraying it in the form of small droplets by means of an agricultural sprayer airblast nozzle type. After tracing, samples of the cloud were taken by means of a filter paper connected with a high volume air sampler.     

Does the interplanetary magnetic field and the solar activity contribute to the tropospheric circulation?

A significant tendency is shown for both Etesians and (+, –) sector boundaries of the interplanetary magnetic field (IMF) to occur on the same solar rotation days, during the main period of the Etesians effect (July–August). In addition, the solar activity seems to control the Etesians distribution within the IMF sector structure. In the epoch of maximum there is a significant tendency of Etesians to occur during toward IMF days. In contrast, in the epoch of minimum Etesians occur mainly during away IMF days. Finally, in the epoch of intermediate the Etesians are uniformly distributed in away and toward IMF days. Since these conclusions are statistically significant at high confidence levels, it is fair to assume that IMF and solar activity seem to contribute, to some extent, to the Etesians occurrences, as well as to their distribution within the solar rotation and the IMF sector structure; that is, some solar contribution to the tropospheric circulation is implied.