Incoherent scatter radar study of the impact of the meteoric influx on nocturnal E-region ionization

We use the Arecibo incoherent scatter radar data collected from 1987 to 199 5 to study meteoric impact on the nocturnal E-region electron/ion content. The nighttime ionization is observed to increase after midnight, which we i nterpret to be due to increase in background meteoric input. The column inc remental rate due to meteoric ionization between 0100 to 0600 LT is estimat ed to be 10(9)/cm(2)/hr. Direct meteoric deposition is responsible for 60% of the total ionization in the morning hours in the altitude range of 97 to 114 km. Although there appears to be an increase in electron content durin g shower periods, there is not an one-to-one relation between meteor shower s and E-region ionization enhancement.