Examination of the oxygen red line signature of a polar cap ionization patch as seen from the Dynamics Explorer 2 satellite

Ground-based observations of polar cap ionization patches have been made for many years. Optical measurements indicate that enhancements occurring in the 630.0-nm emission line are correlated with these ionization patches. The present study examines data from the Fabry-Perot interferometer (FPI) on the Dynamics Explorer 2 spacecraft to determine if patches can be observed optically from space. Since the FPI scanned the forward horizon, it was able to observe the vertical profile of airglow emissions associated with patches, thus giving information about the vertical structure. FPI measurements have been correlated with data from several in situ instruments on the spacecraft. These in situ measurements include electron density, atomic oxygen density, electron temperature, neutral temperature, and electron energy flux. Three polar cap patches have been detected both by the FPI and the in situ instruments. The red line emission patches are enhancements in the 630.0-nm red line in a specific altitude region which create an irregular altitude profile. The red line emission region associated with polar cap ionization patches varies from patch to patch and occurs in the altitude range from below 300 km to 400 km.