Day-time ionospheric disturbances of corpuscular origin in the midlatitudeD-region

¶rt;m uu nau mu m a nu a¶rt;u ¶rt; D-amu u. a¶rt; m nu u u. u¶rt;a a a mu nma u nma mu m (20 ¶rt; 150 ).     

The role of various ionization sources in the A3 lf radio-wave absorption in middle latitudes

Summary The 272 kHz ionospheric absorption has been measured at the Prhonice Observatory by the A3 method (oblique incidence) for a long period. The results of the comparison of these absorption data with indices of solar, geomagnetic and cosmic ray activity are presented for large solar zenith angles. The day-time absorption (x 75° – 85°) is described well by these indices and appears to be affected particularly by direct solar Lyman- radiation. The night-time absorption (x>100°), however, is not described sufficiently by the indices used.     

Relationship between microseisms,geomagnetic activity and ionospheric absorption of radio waves

Summary Relatively good correlation between such remote phenomena as microseisms, geomagnetic activity and ionospheric absorption of radio waves has been observed. These phenomena are probably connected by a considerably increased penetration of energetic particles into the atmosphere under conditions of geomagnetic activity.     

Establishing constraints on groundwater ages with Cl,C, H,and noble gases: A case study in the eastern Paris basin,France

Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using ³H, ¹⁴C and ³⁶Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses.     

Water quality and relationship between superficial and ground water in Rome (Aniene River basin,central Italy)

Chemical, physical, and biological features of streams and ground water of the North-Eastern area of Rome are jointly analyzed in order to assess the status of water resources. Ground water was investigated with classical survey methods (pH, temperature, and electric conductivity). Microbiological pollution, faunal composition, and stream surrounding area conditions of surface waters were studied, in order to quantify the residual value of these ecosystems from both a human and an environmental point of view. Results show a general impairment of the system and the comparison between superficial waters and shallow ground waters makes it possible to detect the presence of a connection between the two levels. This relationship occurs as an exchange from superficial waters (streams and rivers) to the shallow aquifers. Where superficial waters are contaminated, as in the Tor Sapienza stream, pollutants move to the shallow aquifers too, due to the decreased pressure of the over-exploited aquifer. Moreover, uncontrolled drilling activity, diffused in urban areas, makes it possible the connection between shallow and deep ground water. Notwithstanding this, the mixing between superficial and deep ground water system in Rome is not very widespread and, apparently, limited to restricted areas.     

Geometry and Properties of the Excavation-Induced Fractures at the Meuse/Haute-Marne URL Drifts

The performance and safety assessment and technology demonstration are the main objectives of research programs for feasibility studies for deep geological repository of radioactive waste. In this context, the French national radioactive waste management agency (ANDRA) started to develop the Meuse/Haute-Marne underground research laboratory (URL) at Bure, nearly 300 km East of Paris. The host formation consists of a Callovo-Oxfordian claystone found between 420 and 550 m below ground, overlain and underlain by poorly permeable carbonate formations. One of the major concerns related to performance assessment is the excavation-induced fractures which may provide groundwater preferential pathway for radionuclide migration. The extent of the fractures possibly acting significantly in the radionuclide migration is known as the excavation damaged zone (EDZ). A scientific study on the EDZ characterization is performed at the main level of the URL (?490 m). Observations such as structural analysis on core, overcored resin-filled samples, geological survey of the drift face and sidewalls, were made to better understand the fracture network characteristics, extent and its generation. Pulse and constant head test hydraulic conductivity measurements were performed with multi packer system to estimate the extension of the EDZ hydraulic conductivity. Fractures exhibited high transmissivity near the excavation walls, but farther from the exaction walls, shear fractures showed hydraulic conductivity values reflecting values of undisturbed or slightly disturbed rock mass condition. The major findings in terms of geometry and properties of excavation-induced fractures are discussed in detail in this paper. For example, it is observed that the shape of the fracture network depends on the orientation of the drift in relation to the orientation of the in situ stress field.