Tidal activity in the meteor zone over Budrio, Italy

A brief survey is presented of the variations with time and height of atmospheric tides observed at Budrio (45 deg N, 12 deg E) in the wind field between 80 and 110 km altitude during the 1978 to 1982 year period. Variations of amplitude maxima mainly of the semidiurnal tide in the winter data of 1979 and 1980 show periodicities of a few days throughout the observing period. Upward propagation of tidal energy during a stratospheric warming in January 1982 is proposed to be inhibited because of instabilities in atmospheric conditions

Radar observations of the Leonid meteoroid stream in 2001

Results of the Leonid meteoroid stream observed in 2001 are presented. Data have been collected during November 13-23, 2001 by using a forward-scatter radar operating along the two long baselines of Bologna-Lecce (700 km) and Bologna-Modra (600 km). The profile of the reflection time shows a broad component on November 18 in the 00–12h UT time interval with maxima between 09:00h and 11:00h UT. About 90% of the reflection time was recorded at the two receiving stations of Lecce and Modra during the peak hour with an associated mass index of s = 1.72. The flux reached a value of 4.5 × 10−11 m−2 s−1 at the solar longitude 236◦ .09±0◦ .02 (November 18, 9h 30m UT) for echoes with duration T ≥ 1 s corresponding to a limiting mass of m � 10 −5 kg. For longer-duration (T ≥ 8 s) echoes, the main activity peak was found a hour later at the solar longitude 236◦ .13±0◦ .02 (November 18, 10h30m UT), similarly as reported by visual observations. The perspective of high levels of Leonid activity in 2002 is discussed

Ground-based radio observations to probe the ozone content in the meteor region

Radar studies of the plasma irregularities produced by meteoroid ablation provide a powerful diagnostic probe of the Earth's atmosphere. This role is especially important as an inexpensive route for studying several atmospheric processes in comparison with other remote sensing techniques or satellite measurements. Ozone concentration has been indirectly measured in the upper mesosphere/lower thermosphere region by the BLM (Bologna-Lecce-Modra) Forward Scatter (FS) meteor radar by the detection of meteoroids interacting with the Earth's atmosphere. Results of variations of mesospheric ozone concentration at different height levels and time scales were deduced in 1992-2000 from the cumulative duration distributions of overdense echoes. Data of the BLM radar obtained in the last millennium decade confi rm the existence of a secondary ozone layer at atmospheric heights of 85-90 km and show a gradual yearly depletion of the ozone content, similarly to the decrease measured in the eighties by the Solar Mesosphere Explorer (SME) satellite throughout consecutive years (Rusch et al., 1990). Radio observations show in addition large seasonal variations at middle latitudes where the abundance at a secondary ozone maximum at 85-90 km is found to be as much as a factor of two higher in spring months than that in summer months

Approaching deterministic and probabilistic truth: a unified account

The basic problem of a theory of truth approximation is defining when a theory is \u201cclose to the truth\u201d about some relevant domain. Existing accounts of truthlikeness or verisimilitude address this problem, but are usually limited to the problem of approaching a \u201cdeterministic\u201d truth by means of deterministic theories.Ageneral theory of truth approximation, however, should arguably cover also cases where either the relevant theories, or \u201cthe truth\u201d, or both, are \u201cprobabilistic\u201d in nature. As a step forward in this direction, we first present a general characterization of both deterministic and probabilistic truth approximation; then, we introduce a new account of verisimilitude which provides a simple formal framework to deal with such issue in a unified way. The connections of our account with some other proposals in the literature are also briefly discussed

The Leonid meteor shower 1996-2002: Results from forward-scatter radio observations

Results from the observations of the Leonid meteor shower in 1996-2002 by the BLM (Bologna-Lecce-Modra) forward-scatter radio system for meteor observation carried out along two baselines, Bologna-Lecce (Italy)and Bologna-Modra (Slovakia), are presented and discussed. The activity curves of long-duration echoes (≥ 8 s)and their variations indicate multiple peak activity which are attributed to filamentary structure of the stream. The mass distribution exponents in the period of the shower maximum shows significant changes in individual years, with a high contribution of larger particles chiefly in 1998

The orbit, structure and evolution of the Lyrid meteoroid stream

The orbit and structure of the Lyrid meteor stream based on photographic orbits available in the IAU Meteor database are investigated. Seventeen Lyrids were found in the database and the radiant and orbit of the stream were derived. In the stream three very distinct groups of orbits—short-period, longperiod and extreme (hyperbolic orbits), are separated. The mutual consistence of the groups is investigated by following the orbital evolution of individual meteors. The long-period group has the evolution almost identical with that of the parent comet C/1861 G1 Thatcher. The hyperbolic orbits are most probably the result of erroneous measurements

A partial consequence account of truthlikeness

Popper\u2019s original definition of truthlikeness relied on a central insight: that truthlikeness combines truth and information, in the sense that a proposition is closer to the truth the more true consequences and the less false consequences it entails. As intuitively compelling as this definition may be, it is untenable, as proved long ago; still, one can arguably rely on Popper\u2019s intuition to provide an adequate account of truthlikeness. To this aim, we mobilize some classical work on partial entailment in defining a new measure of truthlikeness which satisfies a number of desiderata. The resulting account has some interesting and surprising connections with other accounts on the market, thus shedding new light on current attempts of systematizing different approaches to verisimilitude