Simultaneous ground based observations of an auroral arc in daytime/twilighttime OI 630.0 nm emission and by incoherent scatter radar

We present the ground-based oxygen 630.0 nm daytime optical measurements of a discrete auroral are from Sondre Stromfjord, Greenland. The optical meas urements were made using an imaging echelle spectrograph built at Boston Un iversity. We show that the auroral optical signature extracted from the blu e-sky background agrees closely in both space and time with the aurorally e nhanced electron densities at 200 km altitude obtained simultaneously by th e incoherent scatter radar. The dayglow measurements are also in good agree ment with the integrated emission rates modeled using the measured N-e, T-e , and T-i profiles from the radar. The results reported in this paper demon strate the potential of this spectrograph to observe aurora during daytime, and it promises to be a valuable complement to the existing tools for the investigation of upper atmospheric phenomena.