Simultaneous observations of lower thermospheric composition change duringmoderate auroral activity from Kangerlussuaq and Narsarsuaq, Greenland

To obtain information regarding the spatial scales involved in lower thermo spheric composition changes in the auroral zone, simultaneous observations were carried out using photometers at Kangerlussuaq and Narsarsuaq, Greenla nd, two sites separated by similar to 750 km in distance. At night, Kangerl ussuaq, located at 67 degreesN geographic is most often at the northern edg e of the aurora; oval, while Narsarsuaq, at the southern tip of Greenland, is more often in or at the southern edge of the auroral oval. On January 29 -30, 1998, moderate auroral activity was recorded from both sites. Besides the photometer systems, observations were obtained during part or all of th is period from Polar satellite instruments, from the Greenland magnetometer chain, from the CANOPUS chain of magnetometers and photometers, from DMSP, and from the Sondrestrom incoherent scatter radar. The analysis of these d ata show the necessity of considering both nonlocal and local sources in mo deling aurorally induced changes in lower thermospheric composition.