Il Nuovo Cimento C

Peculiar lunar echoes obtained with a radar operating at 13.866 MHz are presented and discussed. Some of their features are reconduced to a total or to a partial guidance by ionospheric and magnetospheric irregularities aligned with the geomagnetic lines of force. Precisely, such irregularities are intervening as natural wave guides or as leaky-wave antennas. In the latter case they are characterized by very high gains so that one can speak of a sort of focusing. This focusing could be used for the observation of magnetospheric turbulence, could explain some of the solar bursts and could suggest a practical utilization of the round-the-world propagation.

A model to study the annual behaviour of the temperature of a homogeneous solid (considered like a semispace) will be presented in this paper. The model gives the temperature of the solid at any time and at any depth. It assumes the solar flux as the incoming flux, constant atmospheric effects and a simple expression for the outgoing flux. Finally solutions of the soil temperature, when a meteorological transient (box shape) is present, will be shown. The model gives a qualitative behaviour of the soil temperature on a yearly basis and it is like the many experimentally observed behaviours.

Data for the soft X-ray source 1E0630+178 are now available from four independent measurements of the Einstein and EXOSAT missions. These are presented and compared in the light of the different characteristics and energy response of the different X-ray imaging detectors used (IPC, LE 1, LE 2). The time variability on medium (∼ hours) time scale is also investigated.

We show that the frequencies of atmospheric molecular thermal vibrations significantly influence the spectral positioning of the terrestrial window. The bandpass filtering process of this window is confined to the region starting from theE-region and extending to an altitude not exceeding about 600 km. This indicates that a significant part of the infrared radiation emanating from lower altitudes is absorbed directly into the ionosphere. Implicitly, the infrared radiation field as viewed downward from the top of the ozonosphere is continuously «mapped» into the ionosphere in terms of temperature and hence ionization variations. This mapping may be a vital cause of ionospheric irregularities. Factors that influence the transmission coefficient of the terrestrial window are mentioned and discussed. In particular, it is shown that if the terrestrial thermal radiation shifts in response to a temperature change in accordance with Wien's displacement law, the terrestrial window cannot correspondingly shift and continue aligning itself approximately with the peak of the spectrum unless different atmospheric molecules dominate the vibrational process. However, whether different molecules dominate the vibrational process or not, a change in atmospheric temperature makes the transmission coefficient of the window change in the same sense. Consequently, the much reported role played by the window in moderating the temperature of the Earth-Atmosphere system is apparently carried out even when the latter temperature changes provided that the accompanying adjustments do not put the spectral location of the window completely off the terrestrial radiation spectrum. Finally it is shown that if certain substances are introduced in sufficient quantities into the troposphere (in gaseous or aerosol forms), the bandpass filtering process of the terrestrial window may consequently operate in the latter and hence cause regional or global warming.

A synchronized array of fast photomultipliers has been used to reconstruct the image in Ĉerenkov light of individual large cosmicray showers high in the atmosphere. The details of the images are in agreement with simulations based upon conservative models for cascade development. Observation of the fluctuations of the image between showers may enable the mass of the energetic cosmic rays to be determined.

Coherent elastic neutrino scattering on nuclei can only be detected via the recoil energy of the nucleus. We try to develop a detector based on metastable superconducting grains to detect these small recoil energies. Experiments testing some fundamental properties of a detector using metastable Sn and Cd grains are presented. In the case of Cd a sensitivity of at least 24 eV/μm3 (normalized to the volume of the grains) was achieved. We expect a still higher sensitivity if superconductors with very lowT c are used and the quality of the grains (sphericity, size distribution, solid state properties) is improved.