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

Abstract

Abstract. We present the ground-based oxygen 630.0 nm daytime optical measurements of a discrete auroral arc from $ondre Stromfjord, Greenland. The optical measurements were made using an imaging echelle spectrograph built at Boston University. We show that the auroral optical signature extracted from the blue-sky background agrees closely in both space and time with the aurorMly enhanced electron densities at 200 km altitude obtained simultaneously by the incoherent scatter radar. The dayglow measurements are also in good agreement with the integrated emission rates modeled using the measured N,, T,, and Ti profiles from the radar. The results reported in this paper demonstrate 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.

Observations of colocated optical and radar aurora

“…[34] Radar aurora in the absence of optical aurora means that the ionospheric convection electric field exceeds a certain threshold for the two-stream instability, which is not a surprising occurrence in the auroral region. The suppression of the radar aurora inside the arcs meanwhile is an expected consequence of electron precipitation, which closely coincides with the optical aurora and electron density enhancements [Pallamraju et al, 2001]. The enhancement of the ionization changes the ionospheric conductivity and reduces the electric field magnitude to a value below the threshold for the excitation of the two-stream instability.…”

Two components of ionospheric plasma structuring at midlatitudes observed during the large magnetic storm of October 30, 2003

“…During these storms, we used ground‐ and space‐based measurements of the aurora to determine the associated plasma structuring. Ground‐based dayglow observations at Boston University (42.2°N, 71.0°W) were made by HIRISE, a high spectral‐resolution (0.12 Å) imaging spectrograph capable of obtaining daytime airglow emissions despite the bright solar background [ Pallamraju et al , 2001]. Space‐based optical measurements by the GUVI instrument on the NASA TIMED satellite [ Christensen et al , 2003] provide the spectral radiance of the Earth's far ultraviolet airglow in the spectral region from 120 to 180 nm using a cross‐track scanning spectrometer.…”

Solar influence on the O(1D) dayglow emission rate: Global‐scale measurements by WINDII on UARS

“…The daytime airglow is extremely difficult to measure from the ground due to Rayleigh scattering in the atmosphere, thus only very few integrated O( 1 D ) emission rates by ground‐based optical instruments and vertical profiles by rockets were reported [e.g., Pallamraju et al , 2001]. Earlier space measurements of O( 1 D ) profiles were provided by the Atmospheric Explorer satellites (AE‐C and E) from a few orbits in 1970's, which were compared to theoretical modeling [e.g., Hays et al , 1973].…”