An Overview of Thunderstorm-Related Research on the Atmospheric Electric Field, Schumann Resonances, Sprites, and the Ionosphere at Sopron, Hungary

This paper gives a resume of the papers written in English which (a) describe some of the recording instruments in use at the Nagycenk Observatory (NCK) since the International Geophysical Year (IGY 1957–1958) and up to the present time, (b) summarise the most important and different types of observations associated with thunderstorms which have been made there, and (c) discuss their various geophysical interpretations. The paper describes the main results which have been obtained in four areas of thunderstorm associated atmospheric and geospace science within the context of Earth system science. These relate to the following parameters of atmospheric electricity: the vertical electric potential gradient just above the Earth’s surface and the air–Earth current as well as the point discharge current, Schumann resonance (SR) signals of the Earth-ionosphere cavity at 8, 14 and 20 Hz, transient luminous events (TLEs), and some aspects of the behaviour of the ionosphere. Deductions from these data sets are concerned with the global lightning activity and the conductivity of the air, with diurnal, seasonal, annual and long-term variations of the SR amplitudes and resonant frequencies in terms of migrating thunderstorm centres, with transient SR excitations and with sprites and other TLEs, and with ionospheric disturbances. The paper closes with some thoughts on future research directions based on the observations at NCK and Sopron and the results achieved since the IGY.     

Direct gravity formula for the Geodetic Reference System 1967

A Direct Gravity Formula, polynomial in latitude, has been obtained from the series expansion of the closed gravity formula of Somigliana by a telescoping procedure. The use of the 7 coefficient formula gives a result as accurate as the closed expression. With 6 coefficients it gives an order of magnitude better accuracy than that of the widely used Chebyshev approximation and with 5 coefficients a result that is accurate to better than that of the conventional form of computing theoretical gravity. The derived approximation is not only simpler than other forms, but also at least 11 and 17 times faster on the CDC CYBER 74 computer than the Chebyshev approximation and the closed gravity formula respectively. Contribution from the Earth Physics Branch N^o 720.     

Propagation of pressure shocks in radiating fluids with variable transport coefficients

The propagation of pressure shocks in a viscous, heat-conducting, and radiating magnetofluid of finite electric conductivity is studied. The equilibrium diffusion approximation of the radiation field is applied. After determining the velocity of the wave front, a differential equation governing the shock strength during propagation is derived. The effects of radiation pressure, radiation flux, and variation of the transport coefficients on the propagation are examined.     

Amino acids derived from Titan tholins

An organic heteropolymer (Titan tholin) was produced by continuous dc discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mbar pressure, roughly simulating the cloudtop atmosphere of Titan. Treatment of this tholin with 6N HCl yielded 16 amino acids by gas chromatography after derivatization of N-trifluroacetyl isopropyl esters on two different capillary columns. Identifications were confirmed by GC/MS. Glycine, aspartic acid, and alpha- and beta-alanine were produced in greatest abundance; the total yield of amino acids was approximately 10(-2), approximately equal to the yield of urea. The presence of "nonbiological" amino acids, the absence of serine, and the fact that the amino acids are racemic within experimental error together indicate that these molecules are not due to microbial or other contamination, but are derived from the tholin. In addition to the HCN, HC2CN, and (CN)2 found by Voyager, nitriles and aminonitriles should be sought in the Titanian atmosphere and, eventually, amino acids on the surface. These results suggest that episodes of liquid water in the past or future of Titan might lead to major further steps in prebiological organic chemistry on that body.     

Disappearing ionospheres on the nightside of Venus

Instruments on the Pioneer Venus Orbiter have detected a substantial ionosphere on the nightside of Venus during most orbits. However, during some orbits the nightside ionosphere seems to have almost disappeared, existing only as irregular patches of low-density plasma. The solar wind dynamic pressure on these occasions is greater than average. We have correlated data from several instruments (Langmuir probe, ion mass spectrometer, retarding potential analyzer, magnetometer, and plasma analyzer) for a number of orbits during which the nightside ionosphere had disappeared. The magnetic field tends to be coherent, horizontal, and larger than usual, and the electron and ion temperatures are much larger than they usually are on the nightside. We suggest mechanisms which might explain the reasons for the disappearance of the ionosphere when the solar wind dynamic pressure is large.     

Petrographical, geochemical and geochronological constraints on igneous clasts and sediments hosted in the Oligo-Miocene Bakony Molasse, Hungary: evidence for a Paleo-Drava River system

The provenance of igneous clasts and arenitic sediment enclosed within the Bakony Molasse was studied using geochemical and geochronological methods. The majority of igneous clasts were eroded from the Oligocene Periadriatic magmatic belt. A part of the andesite material has Eocene formation age. Rhyolitic pebbles originated from Permian sequences of the Greywacke zone or the Gurktal Alps. Apatite fission track (FT) ages from the sandstone matrix (age clusters at ~75 and ~30 Ma) are typical for the Austroalpine nappe pile and for the cooling ages of Periadriatic magmatic belt. Variscan detrital zircon FT ages indicate source areas that had not suffered Alpine metamorphism, such as the Bakony Mountains, Drauzug and the Southern Alps. Another group of detrital zircon grains of Late Triassic-Jurassic FT age (mean: ~183 Ma) marks source zones with Mesozoic thermal overprint such as the Gurktal Alps and some Austroalpine regions. Zircon grains with Oligocene FT age (mean: ~34.7 Ma) were derived from the Periadriatic intrusives and their contact zones. On the basis of the new data, we propose that the ancestor of the recent Drava River had already existed in Oligo-Miocene time and distributed eroded material of the southern Eastern Alps to the east.     

Planetary ENA imaging: Effects of different interaction models for Mars

We present and compare energetic neutral atom (ENA) images that are calculated from plasma parameters given by three different simulation models of the interaction between the solar wind and Mars. The images are calculated by combining a model for the ion flow with a model of the neutral atmosphere using the cross-sections for the charge exchange collisions. The three ion models are: an empirical model that is based on Phobos 2 measurements; a three-dimensional hybrid simulation; and a three-dimensional MHD simulation. For the empirical and MHD models the images are obtained by integration of the ENA emission along lines of sight to a virtual ENA instrument. In the case of the hybrid model images are obtained by summing the contributions from all ions, whose positions, velocities, and weights are saved in files at regular intervals.Differences between the models can be detected in the images, for example the hybrid model produces ENA emissions from a larger region than the MHD model does. An asymmetry in the oxygen ion density develops in the hybrid model and can be seen in the oxygen ENA images. The images are influenced by finite gyro radius effects, which are included in the hybrid model but not in the other two. The total production rates of hydrogen ENAs are , , and for the empirical, hybrid and MHD models respectively.This study shows the importance of considering both the type of simulation model used and the proper inclusion of relevant physical phenomena and boundary conditions, when modelling the interaction between planets and the solar wind. Although the different models agree fairly well in terms of macroscopic plasma parameters they produce ENA images that differ substantially.