Improved indirect phase reflection height measurements at Panská ves - first results

Summary Indirect phase reflection height measurements have been performed at the Panská Ves Observatory, Czechoslovakia, on two frequencies of 162 (earlier 164) and 153 kHz (earlier 155) for 30 years. However, they were used only for solar flare effect (SFA) monitoring. After introducing new measuring equipment in 1985, the quality of the 162 kHz records became sufficient to apply the indirect phase height analysis (IPHA) method in full. The method itself, the measuring equipment, and the method of evaluation are described in [1]. The purpose of this paper is to describe the first results and to verify the reliability of the 162 kHz IPHA data. The IPHA method as applied to the 162 kHz measurements made at Panská Ves, allows ionospheric and neutral atmospheric parameters to be studied simultaneously and appears to provide reliable and good quality data. The expected seasonal variation and response to sudden stratospheric warmings are observed. The use of the 162 kHz IPHA data in the international MAC/SINE and DYANA campaigns and for monitoring pressure variability at 80 km are briefly described.     

The interplanetary magnetic field sector structure and meteorological microseisms

Summary Meteorological microseisms, recorded at the Prague seismic station and, similarly, at other Central Europe stations, reflect certain meteorological situations in the North Atlantic frontal zone. Meteorological elements in this zone are affected by some factors of extra-terrestrial origin, among others by the interplanetary magnetic field (IMF) sector structure. The analysis of the 68 IMF sector boundary passage effects in microseismic activity, expressed in microseismic amplitudes, showed a well-developed minimum of microseismic activity on the day of the boundary passage in winter, but no such effect in spring and autumn. In spring and autumn, however, a tendency was observed to slightly higher microseismic activity in the away (+) sector, whereas no such tendency was observed in winter. These results agree with the IMF effect found in the troposphere. Generally, the IMF sector structure is only a modulating rather than a major factor controlling the microseismic activity.     

SEA and SDA measurements at panská VES — peculiar Events

Summary The results of the twelve-year (1962–1973)SEA (27 kHz) andSDA (5 kHz) measurements at the Panská Ves Observatory are presented with an emphasis on peculiar events. About half of allSIDs are observed asSEA events and about 10% asSDAs. NoSID has been observed only as anSDA. A fewSIDs have been observed asSEA only, most of them being probably of non-solar origin. A few events observed asSEA andSDA only, or as anSID withSDA, but withoutSEA, are briefly discussed, too.     

Ionospheric effects of the December 16–18, 1971 geomagnetic storm

Summary The post-storm effect (PSE) of the December 16–18, 1971 geomagnetic storm is studied with the use of the ionospheric radio wave absorption measurements and f _min data from a network of the GDR, USSR and Czechoslovak observatories. Only a high latitude effect of the storm was found. We found more significant absorption effects associated with later weaker enhancements of geomagnetic activity. The part played by the interplanetary magnetic field is demonstrated. A magnetospheric explanation of the observed variability of PSE based on the time-development of filling up the slot region is suggested.     

A3 ionospheric absorption measurements on 1539 kHz at Panská Ves

u¶rt;m mam uu u nu a¶rt;u m¶rt;3 (a na¶rt;u) a amm 1539 a amuu aa a nu¶rt; am 1978 — am 1981. u m nuau nu mma. a¶rt;am u¶rt;aa ma (a aumu) u a auau nu, u u aauu u an u u. numa u am au nu ¶rt; =60° na¶rt;am. au naa, m nu u um a a ¶rt;a ¶rt;m a nu¶rt;, nu a m n u nua nu mma am 1980.     

Magma evolution at mount vulture (Southern Italy)

The Vulture complex is made up of foiditic, tephritic, phonolitic-trachytic and phonolitic products. New rock analyses have been performed in order to ascertain whether the various rock types derive from a unique parental magma and, if so, to define its nature. The data presented support that the Vulture suite originated from a foiditic melt which had differentiated at low pressures. The main process determining the foidite → → tephrite → phonolitic trachyte evolution seems to be the crystal fractionation of mainly clinopyroxenes, and opaques, with the contribution of plagioclases and haüyne too in the tephrite → trachyte evolution. Additionary role must have been played by a mixing of melts at different evolution stages occurred in a shallow seated magma chamber.     

Shallow velocity model of the Northern Flank of Stromboli Volcano, deduced by high frequency surface wave dispersion

The wavefield produced by the Stromboli volcano explosion quakes shows a significant amount of surface waves. Rayleigh waves recorded by a linear array have been investigated to infer the shear-wave velocity model of the Stromboli northern flank. The group velocity dispersion curve was obtained using the multiple filter technique, while the phase velocity dispersion curve was calculated both by phase-matched filtering and performing a p– stack on the observed waveforms. Through the inversion of these curves we were able to recover the shear-wave structure to a depth of about 190 m.     

Solar Activity Effects on Gravity Wave Activity Inferred from Radio Wave Absorption in the Lower Ionosphere

The low frequency (LF) nighttime radio-wave absorption in the lower ionosphere has been measured at Prhonice (50°N, 15°E) in central Europe for over 35 years. Digital measurements, performed since summer 1988, allow absorption oscillations in the period range 10 – 180 mins, which are believed to reflect gravity wave activity, to be derived. Unfortunately, problems with the transmitter in recent years terminated the evaluation of gravity wave activity. The analysis of the available information (6 years of data) allows two conclusions to be drawn as to the effects of the solar activity on gravity wave activity: (1) there is no detectable effect of the solar 27-day variation on gravity wave activity; (2) there is an indication that the positive effect of the 11-year solar cycle on gravity wave activity in the winter half of the year is remarkable (lack of data in summer). The result concerning the solar cycle effect is, to a certain extent, preliminary, because the available data do not cover a complete solar cycle. A comparison with results from other stations and an interpretation of results are presented.     

The influence of the angular velocity distribution on the energy transport in the Sun's convection zone

This contribution is a purely exploratory search to investigate the way the distribution of angular velocity inside the Sun's convection zone affects the energy transport. This is related with problems concerning the magnetic activity, whose appearance at the Sun's surface depends on the shape of the isorotation surfaces, and the latitudinal variations in flux. The proposed model is non-linear and axisymmetric.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

Methane and Carbon Dioxide Seasonal Cycles at Urban Brazilian Inland Sites

Methane and carbon dioxide seasonal cycles during years 1998 and 1999 at two Brazilian urban and inland sites are presented. The mixing ratio averages over the studied period of time were 1.80 ppm CH₄ and 384.7 ppm CO₂. A comparison is made between continental averages and theaverages of the three nearest global network background sites of NOAA-CMDL comprising Ascension Island, Namibia and Easter Island. Inland sites had 0.08 ppm or 4.9% more CH₄ and 19.0 ppm or 4.9% moreCO₂ than background over the same time span. The CH₄ summer minimum observed in remote sites was also detected inland. During the month of October 98 and 99 inland mixing ratios were frequently similar to background.