Observing and modelling F-Region ionospheric dynamics using the (OII) 7320 angstroms A emission.

Abstract

Limb-scan observations of Doppler line profiles from the (OII) $\lambda$7320A emission at F-Region altitudes, made with the Fabry-Perot interferometer (FPI) on the Dynamics Explorer-2 (DE-2) spacecraft, have been analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The DE-2 results presented here demonstrate the first spaceborne use of the remote-sensing Doppler technique for measurements of ionospheric convection. The FPI meridional ion drift measurements have been compared with nearly simultaneous in situ ion drift measurements from the Retarding Potential Analyzer (RPA) on DE-2. Once allowance is made for the temporal lag between the in situ and remove measurements, the results from the two techniques are found to be in good agreement, within specified experimental errors, giving confidence in the FPI measurements. The spaceborne interferometric technique has future utility for 2-dimensional imaging of polar ionospheric convection. Results from a simulated space-based observing platform, based on the DE-2 technique and an extension of a 7320A aeronomical model, are presented to demonstrate that a large fraction of the entire polar ionospheric convection pattern can be monitored from space during $\sim$16-minute polar passes of a suitably-instrumented satellite. In the simulation, the polar-orbiting satellite's FPI system views the 7320A emission at various tangent point altitudes at $\pm45\sp\circ$ and $\pm135\sp\circ$ to the satellite velocity vector. By adjusting the horizon scan angle, several swaths of vectors at different horizontal spacing from the satellite can be recovered. Doppler line profiles from the (OII) $\lambda$7320A emission at F-Region altitudes, made with the FPI at Sondre Stromfjord, Greenland, have been analyzed to provide ion drift vectors and temperatures. These measurements demonstrate a unique ground-based use of the remote sensing technique from within the auroral zone since they are compared to simultaneous incoherent scatter radar (ISR) measurements. Results from the two techniques are in reasonable agreement, within specified instrumental errors, giving confidence in ground-based FPI measurements of the high-latitude ionospheric convection pattern and temperature field.