EQUATORIAL IONOSPHERIC ELECTRIC-FIELDS DURING MAGNETOSPHERIC DISTURBANCES - LOCAL TIME LONGITUDE DEPENDENCES FROM RECENT EITS CAMPAIGNS

Data sets collected during a few coordinated Equatorial Ionosphere-The rmosphere System (EITS) observational campaign periods, mainly from th e Brazilian and Asian longitude sectors are analysed in this paper. Io nosonde magnetometer and Ionospheric Electron Content (IEC) data from the EITS-1 and -2 campaigns (during March and December 1991) are compl emented by interplanetary magnetic field and some ground based data se ts from other campaigns. The analysis focuses on the response of the e quatorial ionospheric heights and ionization anomaly to disturbance el ectric fields, identified as a direct penetration electric field assoc iated with IMF B-z changes and development of the ring current (especi ally the asymmetric component), and that produced by a disturbance zon al neutral wind. New evidence on the local time and longitudinal depen dences of these electric fields constitute the main results of this pa per. Especially, a large eastward electric held (associated with the a symmetric ring current) in the dusk-dawn sector causes significant exp ansion of the EIA in this sector, and amplification of the evening pre reversal uplift of the F-layer over Brazil. Significant inhibition of the evening prereversal electric held enhancement seems to be produced by the disturbance zonal wind associated with the magnetic disturbanc es prevailing several hours earlier. Some tentative evidence on the Br azilian dusk sector disturbance field being larger than that of the As ian dusk sector support the existence of a longitude asymmetry in the intensity of the disturbance electric field.