William C. Rideout

Multiradar observations of the polar tongue of ionization

[1] We present a global view of large-scale ionospheric disturbances during the main phase of a major geomagnetic storm. We find that the low-latitude, auroral, and polar latitude regions are coupled by processes that redistribute thermal plasma throughout the system. For the large geomagnetic storm on 20 November 2003, we examine data from the high-latitude incoherent scatter radars at Millstone Hill, Sondrestrom, and EISCAT Tromso, with SuperDARN HF radar observations of the high-latitude convection pattern and DMSP observations of in situ plasma parameters in the topside ionosphere. We combine these with north polar maps of stormtime plumes of enhanced total electron content (TEC) derived from a network of GPS receivers. The polar tongue of ionization (TOI) is seen to be a continuous stream of dense cold plasma entrained in the global convection pattern. The dayside source of the TOI is the plume of storm enhanced density (SED) transported from low latitudes in the postnoon sector by the subauroral disturbance electric field. Convection carries this material through the dayside cusp and across the polar cap to the nightside where the auroral F region is significantly enhanced by the SED material. The three incoherent scatter radars provided full altitude profiles of plasma density, temperatures, and vertical velocity as the TOI plume crossed their different positions, under the cusp, in the center of the polar cap, and at the midnight oval/polar cap boundary. Greatly elevated F peak density (>1.5E12 m 3 ) and low electron and ion temperatures (2500 K at the F peak altitude) characterize the SED/TOI plasma observed at all points along its high-latitude trajectory. For this event, SED/TOI F region TEC (150–1000 km) was 50 TECu both in the cusp and in the center of the polar cap. Large, upward directed fluxes of O+ (>1.E14 m 2 s 1 ) were observed in the topside ionosphere

Signal chain architectures for efficient ionospheric radar processing

Summary form only given. Powerful remote sensing techniques have been developed over the last several decades by the radio science community for probing of the ionospheric plasma state using radio wave scattering combined with passive or active illuminators. The last three decades have seen huge advances in processing and analysis speed afforded by modern specialized and general purpose computing platforms. Accordingly, elements and architectures in a software radar framework have grown to encompass much of the infrastructure used in modern ionospheric sensing platforms. particularly in applications of RF capture, signal processing, and inverse analysis. The dominance of software in these platforms has endowed them with new attributes of greatly enhanced Bexibility and reconfigurability. If managed carefully, these qualities can be used for improved spatial and temporal resolution, while reducing instrumental effects and improving measurement fidelity. Furthermore, streamlined and maximally generic pattern implementations in the design and execution of overall signal processing Bows have the significant advantage of minimizing overhead burdens in implementing new techniques. Finally, these architectures allow for the design of more generic analysis suites which partially insulate the operational facility against RF hardware migrations made necessary by system upgrades and maintenance. We will discuss strategies and implementations for interconnection of key signal pattern elements in the construction of modern software radar signal chains for reliable ionospheric remote sensing. Our philosophy of design encourages clear separation of key boundaries in the signal processing Bow, and speeds coding and debugging by focusing efforts on the essential software radar patterns. It also provides pathways for automated configuration and execution of signal chains for systems with large numbers of RF sensing elements such as phased array configurations. Finally, the presentation will describe a specific implementation of these concepts for a general radar calibration signal chain for incoherent scatter radar platforms, currently under development at the Millstone Hill Geospace Facility.