Negative phases at South-American stations during magnetic storms

Abstract

Ionospheric data at three South-American stations (in low, mid and high latitudes) show negative phases in the high latitude location during magnetic storms. The negative phases in foF2 are caused by changes in the ratio between atomic and molecular concentrations of the neutral atmosphere.
We find that at high latitudes the negative phases are well explained by the [O]/[N ] rate changes. As the latitude decreases, as the wind influence on the F2 layer peak is dominant, the propagation of gravity waves can explain short-lived negative phases. In low latitudes, disturbed thermospheric winds can cause time delays in the normal pattern of foF2, creating alternating positive and negative phases.