[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 À3) 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 À2 s À1 ) were observed in the topside ionosphere from the SED/TOI plume within the cusp.

[1] Recent observations with the new mid-latitude SuperDARN HF radar located at Wallops Island, Virginia have identified a class of ionospheric irregularities that is prevalent in the nightside sub-auroral ionosphere under lowto-moderate Kp conditions. These irregularities can be observed for many hours and generally exhibit very low Doppler velocities. A recent collaborative experiment using the Wallops radar and the Millstone Hill incoherent scatter radar has determined that these irregularities are located at the ionospheric footprint of the plasmapause and in a region of opposed electron density and electron temperature gradients. We conclude that the irregularities are produced by the temperature gradient instability (TGI) or by turbulent cascade from primary irregularity structures produced from this instability. This is the first experimental confirmation that the TGI is effective in producing decameter-scale ionospheric irregularities.

On-orbit firings of both liquid and solid rocket motors provide localized disturbances to the plasma in the upper atmosphere. Large amounts of energy are deposited to ionosphere in the form of expanding exhaust vapors which change the composition and flow velocity. Charge exchange between the neutral exhaust molecules and the background ions (mainly O + ) yields energetic ion beams. The rapidly moving pickup ions excite plasma instabilities and yield optical emissions after dissociative recombination with ambient electrons. Line-of-sight techniques for remote measurements rocket burn effects include direct observation of plume optical emissions with ground and satellite cameras, and plume scatter with UHF and higher frequency radars. Long range detection with HF radars is possible if the burns occur in the dense part of the ionosphere. The exhaust vapors initiate plasma turbulence in the ionosphere that can scatter HF radar waves launched from ground transmitters. Solid rocket motors provide particulates that become charged in the ionosphere and may excite dusty plasma instabilities. Hypersonic exhaust flow Manuscript

Coherent backscatter observations with the Millstone Hill UHF radar (MHR) are used to investigate spatial/temporal variations in the ionospheric sub‐auroral polarization stream (SAPS) electric field. For the 440 MHz MHR, coherent amplitude is on average linearly proportional to electric field strength. The use of both main‐beam and sidelobe returns and the great sensitivity of the MHR system permits observations spanning 3° of the SAPS region with 1‐sec temporal and 10‐km spatial resolution. For a moderately disturbed event on May 25, 2000, the SAPS channel moved steadily equatorward. Large‐scale (30 mV/m peak to peak) wave‐like oscillations in the electric field magnitude (200s–300s periodicity) were seen to propagate across the SAPS channel throughout the hour‐long event. It is suggested that such localized electric field intensifications, which exhibit many of the characteristics of the narrow SAID features described in the literature, arise as wavelike perturbations within the SAPS channel.

Abstract. We describe a novel method for radar ren•ote sensing of the upper atmosphere which relies upon commercial FM broadcasts near 100 MHz. These broadca,sts have high average power and excellent radar ambiguity function. With proper pro•essing we can study the spatial and temporal distribution and Doppler spectrum with excellent and completely unambiguous resolution. Since this passive system has no transmitter, there are enormous benefits in safety, expense, shielding, antenna and receiver design, and licensing issues. Some new problems are introduced, but these are solved with relatively little expense. After presenting the technical basis for such a radar• we describe an instrument that we are building at the University of Washington to study high-latitude plasnxa irregularities in the E region.