[1] Two types of poleward moving plasma concentration enhancements (PMPCEs) were observed during a sequence of pulsed reconnection events, both in the morning convection cell: Type L (low density) was associated with a cusp flow channel and seems likely to have been produced by ionization associated with particle precipitation, while Type H (high density) appeared to originate from the segmentation of the tongue of ionization by the processes which produced the Type L events. As a result, the Type L and Type H PMPCEs were interspersed, producing a complex density structure which underlines the importance of cusp flow channels as a mechanism for segmenting and structuring electron density in the cusp and shows the necessity of differentiating between at least two classes of electron density patches. Citation: Zhang, Q

Abstract. The radars that form the Super Dual Auroral Radar Network (SuperDARN) receive scatter from ionospheric irregularities in both the E-and F-regions, as well as the Earth's surface, either ground or sea. For ionospheric scatter, the current SuperDARN standard software considers a straight-line propagation from the radar to the scattering zone with an altitude assigned by a standard height model. The knowledge of the group delay to a scatter volume is not sufficient for an exact determination of the location of the irregularities. In this study, the difference between the locations of the backscatter echoes determined by SuperDARN standard software and by ray tracing has been evaluated, using the ionosonde data collected at Sodankylä, which is in the field-of-view of Hankasalmi SuperDARN radar. By studying elevation angle information of backscattered echoes from the data sets of Hankasalmi radar in 2008, we have proposed an adjusted fitting location model determined by slant range and elevation angle. To test the reliability of the adjusted model, an independent data set is selected in 2009. The result shows that the difference between the adjusted model and the ray tracing is significantly reduced and the adjusted model could provide a more accurate location for backscatter targets.

Abstract. While the Cluster spacecraft were located near the high-latitude magnetopause, between 11:30-13:00 UT on 1 April 2004, a series of medium to large scale (40 nT, 0.6-1.2 Re) FTEs were observed. During this pass, simultaneous and conjugated SuperDARN measurements are available that show a global flow pattern which is consistent with the expected (mapped) north-west motion of (predominantly subsolar) reconnected, magnetic flux at the magnetopause. We focus on analysing the local response of three FTEs, tracking their magnetopause motion via the four-spacecraft measurements together with their corresponding ground mapped motions. For two of these FTEs, where the tracking is strongly coordinated with the ionospheric flow at each footprint of the implied flux tubes in the Northern Hemisphere, conditions corresponded to stable, increasing (>100 • ) clock angle, while the third event, where the correspondence is less strong, coincided with low (<100 • ) clock angle. Flux tube motion, both measured and modeled from the inferred Xline, qualitatively matches the clear velocity enhancements in ionospheric convections with northward and westward flow at each location in the Northern Hemisphere, measured simultaneously by SuperDARN, and also roughly matches the observed, south-eastward ionospheric flow in the Southern Hemisphere at the time of these events. The time periods of these velocity enhancements infer that the evolution time of the FTEs is about 4-6 min from its origin on magnetopause to its addition to the polar cap. However, the ionospheric response time in the Southern Hemisphere might be Correspondence to: Q.-H. Zhang (zhangqinghe@pric.gov.cn) 2 min longer for the 12:31 UT FTE (and 6 min longer for the 12:51 UT FTE) than the response time in the Northern Hemisphere.

[1] Ground observations of Pc3 ULF waves at high latitude show enhanced pulsation activity near the cusp. To investigate this, typical Pc3 pulsation events from 0920 to 1010 UT on 1 April 2004 have been selected that are simultaneously observed by the Cluster satellites and Zhongshan, Davis, and Mawson magnetometers, Antarctica. When Cluster was located on closed field lines equatorward of the exterior northern cusp, Zhongshan and Davis were near the ionospheric footprint of the southern cusp. Assuming linear phase variation between the four Cluster spacecraft, the Pc3 waves with a frequency of $25 mHz have a wavelength of $5200 ± 2400 km and wave vector directed almost perpendicular to the geomagnetic field (94.6°± 10.4°) pointing toward the Earth. The Pc3 waves are transverse waves over the interval and different from the broadband perturbations and compressional waves generally observed in the cusp and the magnetosheath, respectively. The wave Poynting flux indicates energy is transported predominantly along the magnetic field line toward the ionosphere. These results indicate that Pc3 waves near the cusp are shear Alfvénic waves guided by closed field lines in the low-latitude boundary of the cusp and reflected from the ionosphere. We suggest that the waves may result from incoming compressional fast waves from the upstream solar wind that couple to shear Alfvén waves guided by the magnetic field at high latitudes and excite field line resonance in various harmonics at middle and low latitudes.

[1] Conjugation of geomagnetic field lines at magnetic high latitude is variable, depending on solar wind and interplanetary magnetic field conditions. In this paper the geomagnetic conjugate point of a location under closed field lines near the cusp has been determined dynamically by examining the conjugate phase relation of ultra low frequency (ULF) waves in the Pc5 band using magnetometer data from high-latitude ground stations at Longyearben (LYR), Hornsund (