[1] We present a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011. The radar has a field of view that overlooks the Antarctic Peninsula, a known hot spot of gravity wave activity. We present observations of radar ground-backscatter data, in which the signatures of MSTIDs are manifested as structured enhancements in echo power. Observed periods were in the range 30-80 min, corresponding to frequencies of 0.2-0.6 mHz. Wavelengths were generally in the range 200-800 km and phase speeds in the range 100-300 m s -1 . These values are within the ranges typically associated with medium-scale gravity waves. We find a primary population of northward (equatorward) propagating MSTIDs, which demonstrate an association with enhanced solar wind-magnetosphere coupling and a smaller, westward propagating population, that could be associated with atmospheric gravity waves excited by winds over the Andean and Antarctic Peninsula mountains or by the high winds of the Antarctic Polar Vortex.

We demonstrate that the Super Dual Auroral Radar Network (SuperDARN) radar at Syowa station, Antarctica, can be used to detect high frequency radio wave attenuation in the D region ionosphere during energetic electron precipitation (EEP) events. EEP‐related attenuation is identified in the radar data as a sudden reduction in the backscatter power and background noise parameters. We focus initially on EEP associated with pulsating aurora and use images from a colocated all‐sky camera as a validation data set for the radar‐based EEP event detection method. Our results show that high‐frequency attenuation that commences during periods of optical pulsating aurora typically continues for 2–4 hr after the camera stops imaging at dawn. We then use the radar data to determine EEP occurrence rates as a function of magnetic local time (MLT) using a database of 555 events detected in 2011. EEP occurrence rates are highest in the early morning sector and lowest at around 15:00–18:00 MLT. The postmidnight and morning sector occurrence rates exhibit significant seasonal variations, reaching approximately 50% in the winter and 15% in the summer, whereas no seasonal variations were observed in other MLT sectors. The mean event lifetime determined from the radar data was 2.25 hr, and 10% of events had lifetimes exceeding 5 hr.

Abstract. At 10:00 UT on 14 February 2001, the quartet of ESA Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the post-noon sector on an outbound trajectory. At this time, the interplanetary magnetic field incident upon the dayside magnetopause was oriented southward and duskward (B Z negative, B Y positive), having turned from a northward orientation just over 1 hour earlier. As they neared the magnetopause the magnetic field, electron, and ion sensors on board the Cluster spacecraft observed characteristic field and particle signatures of magnetospheric flux transfer events (FTEs). Following the traversal of a boundary layer and the magnetopause, the spacecraft went on to observe further signatures of FTEs in the magnetosheath. During this interval of ongoing pulsed reconnection at the high-latitude post-noon magnetopause, the footprints of the Cluster spacecraft were located in the fields-of-view of the SuperDARN Finland and Syowa East radars located in the Northern and Southern Hemispheres, respectively. This study extends upon the initial survey of Wild et al. (2001) by comparing for the first time in situ magnetic field and plasma signatures of FTEs (here observed by the Cluster 1 spacecraft) with the simultaneous flow modulations in the conjugate ionospheres in the two hemispheres. During the period under scrutiny, the flow disturbances in the conjugate ionospheres are manifest as classic "pulsed ionospheric flows" (PIFs) and "poleward moving radar auroral forms" (PMRAFs). We demonstrate that the ionospheric flows excited in response to FTEs at the magnetopause are not those expected for a spatially limited reconnection region, somewhere in the vicinity of the Cluster 1 spacecraft. By examining the large-and small-scale flows in the high-latitude ionosphere, and the inter-hemispheric correspondence exhibited during this interval, we conclude that the reconnection processes that result in the generation of PIFs/PMRAFs must Correspondence to: J. A. Wild (j.wild@ion.le.ac.uk) extend over many (at least 4) hours of magnetic local time on the pre-and post-noon magnetopause.

Abstract. The HF radars of the Super Dual Auroral Radar Network (SuperDARN)observe the E x B convective drift, of ionospheric plasma when suitable small-scale field-Migned irregularities (FAI) from which to scatter are present. In order to estimate the distribution of FAIs in the subauroral F region, we have investigated the scattering occurrence percentage using data from six Northern Hemisphere radars during 39 months between July 1995 and September 1998. We have ident, ified a morphological tbature known as the dusk scatter event (DUSE; first reported by Ruohoniemi et al. [1988]) in detail and clarified its relation to the boundaries of the plasma density within the subm•roral F region. In all mont, hs, the DUSE appears within a fbw hours local time on the eveningside of sunset, where the magnetic latitude is slightly lower than the equatorward edge of the m•roral oval, which corresponds to the density-depleted structure known as the midlatitude trough. There exists a clear UT effect in the characteristics of DUSE, such that DUSE is more pronounced tbr UTs corresponding to dusk on the prime magnetic meridian (0 ø geomagnetic longitude). Furthermore, an enhancement of scattering occurrence around sunrise within t, he trough, which is termed dawn scatter event, (DASE), was newly identified. The region where the DUSE or DASE occurs has a close relationship with the duskside and dawnside ends of the midlatitude trough in the longitudinal direction (which are termed the sunward edges of the trough in this paper), where sunward directed steep plasma density gradients exist. The Kp dependence of the scattering occurrence was also examined. In disturbed conditions, the DUSE appee[rs at, earlier local times compared with that in quiet conditions, which is consistent with the Kp dependence of the sunward edge of the trough. Three models based on the gradient drift, instability were discussed. It, was tbund that the model which is based on the sunward plasma densit, y gradient at the sunward edges of the midlatitude trough and ambient electric field is most favorable tbr the growth of FAIs in this region and can consistently explain the statistical tbat, ures of DUSE and DASE. These facts indicate that we can est, imat, e t, he longitudinal extent of the midlatitude trough fi'om the appearance of DUSE and DASE observed by SuperDARN. In this study we exten(t the work of Ruoh, on'ie'mi et al.