Planetary wave-type oscillations in the ionosphere and their relationship to mesospheric/lower thermospheric and geomagnetic disturbances at Wuhan (30.6°N, 114.5°E)

Abstract

Using wind, ionospheric and geomagnetic intensity data observed simultaneously at Wuhan (30.6°N, 114.5°E) in 2002 and 2003, planetary wave type oscillations (PWTO) in the ionosphere and their relationship with oscillations in the mesosphere/lower thermosphere (MLT) and geomagnetic intensity have been investigated. Two cases of 2- and 5-day oscillations in the ionosphere are analyzed to distinguish MLT drivers and geomagnetic drivers. The geomagnetic oscillations are the most important drivers for the PWTO with dominant periods of 5-, 10-, 13.5-day. But the planetary waves in MLT winds are the main drivers for the quasi-2-day oscillations in the ionosphere. The correlation coefficient of the occurrence rates of the 2-day oscillation in winds and in ionospheric f 0F 2 is 0.82 for the data from February to November. The oscillations in the geomagnetic intensity can drive 30–50% of 5-, 10- and 13.5-day PWTO events in the ionosphere. If we evaluate all of the possible events driven by geomagnetic oscillations, more than 70% of the events have a relationship with geomagnetic oscillations with 5- and 10-day periods. The 39.7 h PWTO in ionospheric plasma frequencies observed from day 161 to 166 in 2002, are generated by an upward propagating wave with period 43.8 h. Two events of 6-day oscillations in the ionosphere observed during May to July in 2003, have different drivers. The first one is probably generated by 5.4-day upward propagating waves in MLT winds, but enhanced during a moderate geomagnetic storm. The second one is generated by the geomagnetic oscillations during a strong geomagnetic storm.