Abstract
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.
Highlights
The interplanetary material which falls on the Earth each year is estimated to be between 150 000 and 220 000 t
Our results show that the hourly rates of meteor echoes may be influenced by the changing angle between the meteor shower radiant and Geminids 1996-2000 BLM radar data
By analyzing our BLM radar data, we found an increase in the relative proportion of long-duration echoes from sporadic background in the daytime over comparable rates in the dark hours
Summary
The interplanetary material which falls on the Earth each year is estimated to be between 150 000 and 220 000 t. Meteoroids – a conspicuous part of the interplanetary matter – are natural impactors contributing to the low Earth space particulate environment. These objects are the products of a series of dynamical and physical processes involving the planetary sciences, because they are strictly connected to the evolution of the minor bodies of the Solar System, asteroids and comets. Radar systems operating in the frequency range 2-100 MHz have been employed for general studies of meteoric ionisation both as probes of atmospheric aeronomy and dynamics or for astronomical information about meteoroids. According to Allen et al (1984), ozone in the terrestrial atmosphere between the stratopause (50 km) and the homopause (100 km) affects: i) the thermal structure and dynamics of the upper atmosphere and its state of ionization ( in the D region); ii) the chemical evolution of the whole atmosphere on geological times; iii) the upper stratospheric ozone layer and the evolution of the terrestrial ecosystem; iv) the clarity in long range evolution; and (v) the operations of low earth-orbit satellites)
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