Evidence for the tongue of ionization under northward interplanetary magnetic field conditions

The activities of the International Ionospheric Tomography Community open up new possibilities of simultaneously imaging the large‐scale spatial structure of the ionosphere in different longitude sectors. In the study, tomography receiver chains in Scandinavia and Greenland were used to provide a wide view of the plasma density structure in the winter, magnetic postnoon sector under conditions of stable, positive interplanetary magnetic field B z component. The spatial distributions of the plasma are discussed in light of a high‐latitude plasma convection pattern pertinent to the conditions, which is supported by DMSP flow measurements. The observations are consistent with a tongue of dayside photoionization being drawn antisunward by the convection pattern to form an arc of enhanced plasma density around the periphery of the polar cap.