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Abstract: We present coordinated optical and radar observations using the Poker Flat Incoherent Scatter Radar (PFISR) in Alaska and the Sondrestrom radar in Greenland. Several cases were examined where intense, similar-looking dynamic auroral structures were observed in the magnetic zenith. The presence or absence of Naturally Enhanced Ion Acoustic Lines (NEIALs) was investigated in both sets of radar data. In all cases, the aurora exhibited small-scale ( –1km), dynamic features that were observed with both all-sky and narrow-field of view (19°) imagers. In all of the cases examined, the PFISR radar observed NEIALs while the Sondrestrom radar did not, despite similar auroral morphology. The main difference between the radars, namely the probing wave number, provides strong evidence for a limiting spatial scale of between 10 and 15cm for the enhanced wave activity responsible for NEIALs. This has implications for constraining the models of NEIAL generation mechanisms. [Copyright &y& Elsevier]

Abstract: Coordinated Poker Flat Incoherent Scatter Radar (PFISR) and imaging observations are examined in order to study the radar scattering signatures of optically visible meteors. Preliminary observations in 2006 revealed that optical meteors were detected by PFISR. A recent campaign in the winter of 2009, employed a radar mode optimized for meteor Doppler shifts. This paper presents a case study from 21 January 2009. Seven out of the 338 meteors observed with PFISR were also detected optically. Six out of those seven were detected by the side lobes of the radar and not the main beam. A positive correlation was found between the corrected backscattered radar power and the optical brightness of the meteors, as well as between optical brightness and absolute speed. Meteors originating in the east had higher speeds and more glancing incidence angles, while meteors originating in the north had lower speeds and more direct incidence angles. [Copyright &y& Elsevier]

Abstract: Previous observations have shown that pulsating aurora sometimes occurs with patches of a vertical extent that is thinner than would be expected for aurora caused by collisional processes, implying that local ionospheric processes are important in causing the narrow luminosity enhancement. However, Poker Flat Incoherent Scatter Radar (PFISR) data from four pulsating aurora events, during the Rocket Observations of Pulsating Aurora (ROPA) mission in January and February 2007, show that the electron density profile associated with the pulsating patches had a thickness of in all four cases and that, therefore, these are not examples of such thin enhancements. A numerical model of the associated volume emission rates for the night of the ROPA launch supports this conclusion. In the process of modeling the volume emission rates, the PFISR data are inverted to calculate the associated electron energy distribution for comparison with in situ electron measurements from ROPA and the REIMEI satellite. The modeled distribution shows a diffuse plasma sheet population which gradually decreases in energy over the course of the event, resulting in precipitation by the end of the PFISR data interval, in agreement with the ROPA/REIMEI measurements. [Copyright &y& Elsevier]