Studies of Plasma Irregularities and Convection in the Polar Ionosphere Using HILAT, SABRE and EISCAT

A statistical study of the F-region main ionospheric trough has been undertaken with EISCAT common programme data to assess the possibility that the trough region is a perferntial region for the generation of E-region irregularities. Three years of CP-3 data from EISCAT formed the basis of this study. Backscatter observed by the coherent radar, SABRE, was also utilised to study the occurrence of irregularities in the E-region. On 26 out of the 36 day s when the trough was observed by EISCAT, SABRE observed coherent backscatter. Although this percentage seems high, there was no consistent relationship between the latitude of the trough minimum and the latitude of peak backscatter intensity. A case study involving a four day run of EISCAT in September 1986 indicates that the trough latitude can be affected by changes in the Interplanetary Magnetic Field north-south components. On two days rapid decreases in the latitude of the trough were related to a southward turning of the IMF and the onset of backscatter. The high percentage of occurrence of and backscatter if believed to be caused by enhanced convection.