MULTI-INSTRUMENT GROUND-BASED OBSERVATIONS OF A TRAVELING CONVECTION VORTICES EVENT

A coordinated ground-based observational campaign using the IMAGE magn etometer network, EISCAT radars and optical instruments on Svalbard ha s made possible detailed studies of a travelling convection vortices(T CV) event on 6 January 1992. Combining the data from these facilities allows us to draw a very detailed picture of the features and dynamics of this TCV event. On the way from the noon to the drawn meridian, th e vortices went through a remarkable development. The propagation velo city in the ionosphere increased from 2.5 to 7.4 km s(-1), and the ori entation of the major axes of the vortices rotated from being almost p arallel to the magnetic meridian near noon to essentially perpendicula r at dawn. By combining electric fields obtained by EISCAT and ionosph eric currents deduced from magnetic field recordings, conductivities a ssociated with the vortices could be estimated. Contrary to expectatio ns we found higher conductivities below the downward field-aligned cur rent (FAG) filament than below the upward directed. Unexpected results also emerged from the optical observations. For most of the time ther e were no discrete aurora at 557.7 nm associated with the TCVs. Only o nce did a discrete form appear at the foot of the upward FAG. This aur ora subsequently expanded eastward and westward leaving its centre at the same longitude while the TCV continued to travel westward. Also we try to identify the source regions of TCVs in the magnetosphere and d iscuss possible generation mechanisms.