An equatorial plasma bubble (EPB) event, emerging near dawn and developing after sunrise, was simultaneously observed by an all-sky imager and the global navigation satellite system (GNSS) network. The observed EPBs showed westward drifts, different from post-sunset EPBs. The EPBs occurred in the recovery phase of a geomagnetic storm, possibly playing a key role in initializing their developments. The results provide a new perspective of EPBs, enriching our knowledge of ionospheric irregularity.

The seasonal variations in the mesopause densities, especially with regard to its global structure, are still unclear. In this study, we report the climatology of the mesopause density estimated using multiyear observations from nine meteor radars from Arctic to Antarctic latitudes. The results reveal a significant AO and SAO in mesopause density, an asymmetry between the two polar regions and evidence of intraseasonal oscillations (ISOs), perhaps associated with the ISOs of the troposphere.

Two traveling ionospheric disturbances (TIDs) were observed by the GPS network in Asia following the large meteorite blast over Chelyabinsk, Russia. No TIDs propagating in a global range were found. Features of TIDs were compared with those excited by early nuclear explosion tests. It is inferred from our analysis that the energy release of the Chelyabinsk meteorite blast may not be large enough to excite such ionospheric disturbances in a global range as some nuclear explosions have done.

A series of interplanetary coronal mass ejections in the period 7–17 March 2012 caused geomagnetic storms that strongly affected the high-latitude ionosphere in the Northern and Southern Hemisphere. Interhemispheric comparison of GPS phase scintillation reveals commonalities as well as asymmetries, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are primarily caused by the dawn-dusk component of the interplanetary magnetic field.