Manifestations of field-aligned currents in tomographic observations of the ionospheric F region

Abstract In November 1995, observations of the ionospheric F region were made in Scandinavia by means of a tomographic chain extending from the south of Finland to the north of Norway. These observations revealed F region structures which, using optical satellite images and ground-based magnetometer data, are interpreted as manifestations of field-aligned currents in the ionospheric F region electron density. A field-aligned plasma enhancement extending to about 700 km altitude is sometimes seen in connection with an upward current, whereas a larger plasma enhancement with an elevated F layer peak altitude is found to lie close to the region of downward current.