Electron loss and meteoric dust in the mesosphere

The ionosphere is always assumed to contain equal numbers of positive and negative charges in a given volume (quasineutrality). Hence fewer electrons than positive charges are an indication of negative charges other than electrons. Theories predict and in-situ mass spectrometer measurements confirmed that these negative charges are negative ions, but recent experimental results suggest that other scavengers of free electrons can also be active in the mesosphere. Outside the polar summer mesosphere this additional removal of electrons is today believed to be due to meteoric dust, which maximises in the mesosphere. Data predominantly from the recent ECOMA flights are used to test this presumption. Six sounding rockets carried different dust detectors, as well as probes for electrons and ions. With such an instrumental ensemble one can assess whether indeed the existence of meteoric dust removes more electrons than would be expected from gas phase ion chemistry alone. Other factors potentially impacting on electron removal are also discussed in the paper.