Travelling ionospheric disturbances behave like waves in the ionosphere, the ionised upper part of the atmosphere. In this study, we use an ionospheric tomography technique to map the electron content as affected by the passage of a large-scale travelling ionospheric disturbance launched during the largest geomagnetic storm observed by modern instruments. This is the first such imaging using this software and to the authors' knowledge the first study of this travelling ionospheric disturbance.

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.