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Ionization changes in the lower ionosphere during the solar eclipse of 7 March 1970

Journal of Atmospheric and Terrestrial Physics
Publication Date
DOI: 10.1016/0021-9169(72)90150-x


Abstract Measurements in the lower ionosphere (65–150 km) of 2.66 MHz differential absorption and of Langmuir probe currents were obtained using four rockets launched in Nova Scotia, Canada during the 7 March 1970 solar eclipse. It was found that the eclipse caused a maximum decrease in the electron number density by more than a factor of 10 below 80 km, but by only 3–5 above 85 km. Below 80 km, the smallest densities were observed on the third flight, 7–20 s after 3rd contact, and the D-region ledge between 65 and 75 km had disappeared. On the last flight, 360 s later, this ledge had begun to redevelop; however, the lowest densities in the 85–90 km and 125–150 km ranges were observed on this flight. Densities of about 60 electrons cm −3 at 80 km, 700 at 85, 7000 at 95 and 30,000 above 105 km were the minimum ones recorded. The paper compares these electron number densities to those measured at night by other experiments. The height dependence of the rate of disappearance of electrons leads to values of the effective recombination coefficient which decrease from about 10 −4 cm 3 s −1 at 80km to 3 × 10 −7 cm −3 s −1 at 95 km and indicates an increase in the ratio of negative ions to electrons below about 80 km.

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