Observations of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power high frequency HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating Magnetized Stimulated Brillouin scatter MSBS and Stimulated Ion Bernstein scatter SIBS in the SEE spectrum. Narrowband SEE features have not been observed at EISCAT before. Narrowband MSBS spectrums are compared to such behavior previously observed at HAARP. Preliminary analyses of SEE data show observation of ion acoustic emission lines due to stimulated Brillouin scatter during the 2012 July EISCAT campaign. For varying heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics whereas electron temperature enhancement weakens measured by EISCAT/UHF radar.

We present a study of ionospheric and thermospheric response during a November 9–10, 2004 major geomagnetic storm event (DsT ∼−300 nT). We utilize the North American sector longitude chain of incoherent scatter radars at Arecibo, Millstone Hill, and Sondrestrom, operating as part of a coordinated international mesosphere/lower thermosphere coupling study experiment. Total electron content (TEC) determinations from global positioning system (GPS) ground receivers, ground magnetometer traces from the Canadian CANOPUS array, Defense Meteorological Satellite Platform (DMSP) topside data, and global convection patterns from the SuperDARN radar network are analyzed to place the detailed radar data in proper mesoscale context. The plasmaspheric boundary layer (PBL) expanded greatly in the dusk sector during ring current intensification to span more than 25° of magnetic latitude, reaching as far south as 30° invariant latitude. Strong sub-auroral polarization stream velocities of more than 1 km/s were accompanied by large upwards thermal O+ fluxes to the overlying magnetosphere. The large PBL expansion subsequently exposed both Millstone Hill and Sondrestrom to the auroral convection pattern, which developed a complex multicell and reverse convection response under strongly northward IMF conditions during a period of global interplanetary electric field penetration. Large traveling atmospheric and ionospheric disturbances caused significant neutral wind and ion velocity surges in the mid-latitude and tropical ionosphere and thermosphere, with substorm activity launching equatorward neutral wind enhancements and subsequent mid-latitude dynamo responses at Millstone Hill. However, ionosphere and thermosphere observations at Arecibo point to significant disturbance propagation modification in the post-dusk sector PBL region.

Recent expansion of the SuperDARN network to midlatitudes and the addition of a new high-time resolution mode provides opportunities to observe mid-latitude ULF waves and other ionospheric sub-auroral features. During a substorm on 22 February 2008, Pi2 pulsations with a period of 172 s were observed simultaneously by the Blackstone, VA SuperDARN radar and magnetometers around the globe. Very similar pulsations were detected by the BKS radar and a nearby magnetometer at Remus, MI, which suggests that a single source generated the Pi2. Due to the localized nature of the radar measurements, the radar data contains significantly more spatial and temporal structure than data recorded by the magnetometers. A cross-phase analysis of magnetometer data places these measurements in the vicinity of the ionospheric projection of the plasmapause. About one minute prior to ground Pi2 onset, two Earthward-moving BBFs were observed by the THEMIS D and E probes in the near-Earth plasma sheet. Based on observations and previous studies, we suggest that the observed Pi2 pulsations are the result of either a plasmaspheric surface wave or a direct compressional response due to the braking of the BBF on the inner magnetosphere.