Plasma Density and Temperature Measurements in the Cusp Ionosphere

A Black Brant X sounding rocket (NASA 35.033) was launched on December 14th, 2002 at 11:16:48~UTC from Ny Ålesund, Norway to study the electrodynamics of the cusp ionosphere and the open/closed field line boundary region. The launch was coordinated with satellite measurements and with optical and radar ground-based observations. The rocket was launched during Bz southward conditions and reached an apogee of 771 km, well above the F-layer peak. Measurements by a fixed-bias (ion) Langmuir probe and a swept Langmuir probe on the rocket payload provide plasma density, density fluctuations, and electron temperature, as well as the plasma potential. The swept Langmuir probe used a 2.5 cm diameter titanium nitride coated spherical electrode whereas the fixed bias probe used a 10 cm diameter, 6.4 mm thick ring as the active element. On the upleg of the rocket trajectory, a very disturbed ionosphere was encountered, with large amplitude (>20%), large scale (typically 10 m-10 km) irregularities superimposed on the background, indicative of the open magnetic field line cusp environment. By contrast, the downleg profile shows a smooth density profile without irregularities that is consistent with the dayside ionosphere on closed magnetic field lines. Elevated electron temperatures were observed coincident with regions of energetic precipitations. These may have been due to instrumental effects, however, and a detailed analysis is still underway. We compare both the density and temperature measurements gathered with the rocket instruments with those measurements simultaneously gathered with the EISCAT radar, and with temperatures derived from the Calgary Suprathermal Ion Imager, that was also part of the rocket payload.