IMAGING OF FIELD-ALIGNED STRUCTURES IN THE AURORAL IONOSPHERE

Tomographic images are presented from a co-ordinated experimental camp aign held in Scandinavia in October 1993. In addition to the five sate llite receiving stations, the EISCAT incoherent scatter radar was used in a special mode (SP-UK-BLOB) to provide independent verification of the tomographic images. The radar was used in this interactive made t o follow the meridional development of a very steep field-aligned grad ient at the poleward edge of a deep trough. Irregular structuring on a scale of tens of kilometres was observed as the feature was followed during a 7-hour run, under very quiet geomagnetic conditions. Several satellite passes were monitored during the run, with the total electro n content measurements being used to reconstruct tomographic images of electron density. Comparison of the images with the EISCAT measuremen ts in the vicinity of the trough wall shows that the field-aligned str ucture is well replicated by the tomographic method. The auroral E-lay er evident in the EISCAT observations has also been imaged by tomograp hic means for the first time.