Radio tomographic imaging of the northern high-latitude ionosphere on a wide geographic scale

Several chains of receivers, measuring total electron content (TEC) during passes of satellites in the U.S. Navy Ionospheric Measuring System (NIMS), are operated at northern high latitudes by members of the International Ionospheric Tomography Community (IITC). Results are presented here of nearly simultaneous latitude-altitude images of the ionosphere over Scandinavia, Greenland, and Alaska, generated from IITC data obtained on 20 September 2001 and interpreted in the context of an IMF-dependent convection model. The images are compared with output from a coupled thermosphere-ionosphere-plasmasphere model and also with maps of high-latitude TEC generated from GPS measurements. With B _z and B_y both weakly negative, the images and map reveal plasma features of a two-cell convection pattern rotated slightly to earlier local magnetic times. The tomographic images provide details of map features such as a tongue of ionization created by solar EUV radiation on the dayside and entrained by convection into the polar cap from the western Russian sector. Combining latitude versus altitude tomographic images generated in different longitudinal sectors from polar-orbiting beacon satellites such as those of NIMS with TEC maps from GPS offers an emerging opportunity for polar aeronomic studies, especially if further related to synoptic convection measurements. The results also demonstrate the potential role of wide-scale radio tomography in the verification of ionospheric models.