[en] A statistical analysis of 90 selected ionospheric storms has been carried out from MUF(ZERO)F₂ and MUF(3000)F₂ measured in Italy from 1958 to 1972. Typical behavior with regard to season, storm intensity, and statistical dispersion is shown for forecasting purposes. (auth)

[en] Some results of statistical analysis on data from the Rome ionosphere station during the period 1948-1983 are showen as a model of the normal ionosphere over Rome

[en] A study is made of the F2-layer effect of magnetospheric substorms over the Mediterranean area using data from several ionospheric stations for selected events in the current sunspot cycle 21. The night-time enhancements in the critical frequency of the F2-layer (f₀F2) and the total electron content (TEC) have been found with both premidnight and postmidnight f₀F2 peaks and a subsequent decrease in the minimum virtual height of the F region (h'F). It is found that the enhancements occur through the nights under steady geomagnetic conditions and that the time at which it is seen at Rome and Grocka ionospheric stations is progressively earlier as geomagnetic activity increases. It has been further shown that this type of the f₀F2 night-time increases is not always accompanied by an increase in TEC, although the reverse holds true during the nights of increased substorm activity. The fact that the considerable variability in f₀F2, TEC and h'F at the onset of the substorm expansion are preceded by the ionospheric dynamics associated with these observations can be very useful in the identification of precursor indicative of short-term variations of ionospheric propagation conditions

[en] The low frequency facility, a Virgo R and D experiment, is composed by a Fabry-Perot cavity attached and controlled by the Virgo suspension; the goal is to measure the thermal noise of the apparatus above 10 Hz, with a displacement sensitivity as high as 10^-18 m/√Hz. Since September 2001 the apparatus, located inside the INFN-Pisa experimental area, has been completely built and put into operation. Vacuum facilities and the control loops have been set up. Transfer functions, necessary to control the cavity, absolute test mass displacement and the first demonstration of the cavity locking are reported

[en] In this work, we estimate the performance of a method for the detection of burst events in the data produced by interferometric gravitational wave detectors. We compute the receiver operating characteristics in the specific case of a simulated noise having the spectral density expected for Virgo, using test signals taken from a library of possible waveforms emitted during the collapse of the core of type II supernovae

[en] In the energy region 10 - 100 TeV both the c.r. composition from direct measurements and the cross section for high energy secondary production in the very forward region for p-air interactions are rather uncertain. Contemporaneous measurements of the total energy and of the threshold energy/nucleon of the primary particle can be provided by the atmospheric Cherenkov light and high energy muons. These measurements are performed by the combined operation of the Cherenkov array of the EAS-TOP experiment on the surface (810 gcm² atmospheric depth) and of the LVD experiment in the underground Gran Sasso Laboratories (3300 m w.e.; E^th_μ = 1.3 TeV) leading to the measurement of < N_μ > (E_μ > 1.3 TeV, E₀) in the given energy range. The combined operation of the experiments and preliminary results are reported

[en] The low frequency facility is a VIRGO R and D experiment having the goal of performing a direct measurement of the thermal noise of the VIRGO suspensions by means of a two-mirror Fabry-Perot cavity suspended to the last stage of the attenuating chain. The present status of advancement of this experiment is reported: the apparatus, including mechanical and optical parts, has been completely built and put into operation. Vacuum facilities and the first control loops are active. First measurements on the suspended cavity are in progress