A worldwide study of the H, D and Z variation On Abnormal Quiet Days (AQDs)

An extensive analysis, using 80 stations, has been made of the latitudinal and longitudinal variation of the additional fields in H, D and Z that occurred on Abnormal Quiet Days (AQDs) during the Northern Hemisphere winter months in the years 1964–65. This analysis shows that the additional fields occurring on AQDs may be represented by a single-current vortex (SCV) that has a focus in the latitude range 15–20°N for the Northern Hemisphere winter AQDs. the evidence strongly suggests that the most likely location of the SCV is the ionosphere, although no further insight into what drives it is forthcoming.