Structural aspects of meteoroid streams observed by a forward scatter radar system

Forward scatter (FS) continuous wave (CW) meteor radar observations carried out during 1992–96 over the long baseline Bologna–Lecce in Italy, enable us to investigate the structure of the main meteoroid streams and of the sporadic background by the cumulative distributions vs durations of the recorded echoes. The trends of the mass-distribution of particles belonging to the quoted meteor complexes are discussed in terms of variations of the mass index s against echo durations and in terms of steady-state conditions for each meteor population. The mass index values of the sporadic background are generally higher than for meteor showers in the duration range of 0.1≤T≤10 s. ational evidence indicates that the combined cumulative distributions of meteor trails vs peak signal amplitudes and vs durations represent a more sensitive indicator of the meteoroid stream activity, and consequently, of the mass-index variation. The unexpected high proportion of short-lived echoes which produce very faint meteors is interpreted in terms of fragmenting particles which form filaments younger than those present in other parts of the stream. The effects of non-gravitational forces as the solar radiation pressure, the Poynting–Robertson (P–R) effect, mutual collisions, etc., are taken into account to justify the observed widespread radiants and unstable populations of particles.