Radar Observations of Structured Plasma in the High-Latitude F Region

摘要

Results are presented from a campaign of coordinated measurements between the Chatanika radar and the TRIAD satellite to investigate the production mechanisms responsible for localized high-latitude scintillation. The radar measured that latitudinal variations of plasma density and electric field while the satellite measured the latitudinal variation of field-aligned current. This information was used to assess the stability of the observed plasma configuration. Field-aligned ionization enhancements or plasma 'blobs' with steep poleward and equatorward edges were found to be a common feature of the midnight-sector auroral F region. Their presence is not strongly related to magnetic activity nor to E-region processes. The plasma blobs are unstable to the current convective instability with growth rates of several millihertz. They are unstable to the gradient drift instability on either the poleward or equatorward edge, depending on the electric field and neutral-wind configuration. Field-aligned currents have a further destabilizing influence, but seldom (if ever) dominate the electric-field contribution to instability. The presence of plasma density irregularities associated with the blobs were verified by observing scintillation on the TRIAD satellite telemetry signal at 150 MHz. The F-region irregularities exist despite the presence of a highly conducting auroral E region to which the F-region plasma is connected by the geomagnetic field lines. The F-region blobs and their associated irregularities convect with the background electric field.