Abstract:
The mid-latitude upper atmosphere is directly affected by the inner magnetosphere through the interactions at the closed geomagnetic field line boundary. Several space weather phenomena associated with magnetospheric-plasmaspheric exchanges can be mapped to mid-latitudes. One such phenomena that occurs over mid-latitudes during geomagnetic storms is the storm enhanced density (SED). So far, storm time ionospheric features have been studied primarily using radar, GPS and in situ measurements. We present high spectral resolution ground-based measurements of OI 630.0 nm dayglow emissions obtained from Boston to investigate thermospheric behavior during both geomagnetic quiet and disturbed times, as these are very sensitive to changes in the ionospheric plasma temperatures, and densities. During a geomagnetic storm on 7-9 Nov 2004 (Kp = 9-), an anomalous enhancement in brightness (>1 kR) was observed in the dayglow for about an hour duration near local sunset (dusk hours), which was not seen on other neighboring days. This enhancement in OI 630.0 nm dayglow observed on 9 Nov 2004 is confirmed to be a SED event as seen from the complimentary datasets, the Millstone Hill incoherent scatter radar (ISR), Defence Meteorological Satellite Program satellite and GPS total electron content. Further, model estimates of OI 630.0 nm dayglow intensities using ISR measured electron/ion temperature and electron densities as inputs show good agreement with our measurements. These results make this study possibly the first report on the daytime optical signatures of SED.