CHEMICALLY DEPLETED F-2 ION COMPOSITION - MEASUREMENTS AND THEORY

The Lagopedo experiments were the first in situ ion composition measurements of a chemically modified ionosphere. An artificial ionospheric hole was produced by the injection of H//2O and CO//2 into the O** plus dominant F//2 region. These released chemicals increased the natural ionospheric depletion rate by approximately two orders of magnitude by changing the rate of molecular ion formation. As the rocket payload passed through the event cloud, O** plus was observed at a reduced density, and H//2O** plus , H//3O** plus , and O//2** plus were observed in enhanced amounts that varied with time after and distance from the event. H//3O** plus was dominant at times immediately after the event, when the neutral water density was high, but rapidly decreased to 20-40% of the H//2O** plus . A computer model simulated the postevent O** plus and O//2** plus distributions well, but it had mixed success with the H//2O** plus and H//3O** plus distributions. Measurable changes in ion composition levels were detected up to 40 km from the release point.