Travelling disturbances associated with ionospheric storms

Following each of three geomagnetic sudden commencements, ionospheric disturbances (ionospheric storms) are found to propagate from two isolated locations in high-latitude regions of the Earth. These two positions are conjugate points (magnetically), and are in different locations for each magnetic storm. Speeds of travel are 361 m/sec and 722 m/sec. Disturbances with the slower speed produce detectable effects on the ionosphere after encircling the Earth. I.G.Y. data (hourly values of h′F) from a world-wide station network were used and a superposed-epoch method employed. A study of ionograms from Australian stations during these and other magnetic storms supports the superposed-epoch results. It is shown that red arcs, certain auroral forms and v.l.f. electromagnetic emissions may be associated with these travelling disturbances