Active Plasma Experiment: North Star Particle Data

We report on data from particle instruments making in situ sounding rocket measurements of the particle environment within and near an aluminum plasma jet caused by an explosion in the auroral ionosphere. The Active Plasma Experiment sounding rocket was launched to an altitude of 350 km from the Poker Flat Research Range in January 1999. The payload separated after launch into observing payloads and two explosive plasma jet generators. During the flight, the two explosive packages were detonated, and the observing payloads studied the surrounding environment. The particle instruments measured the resulting plasma jet from a distance of approximately 500 m. The instruments measured ions from 10 to 420 eV, electrons from 10 to 6000 eV, and low-energy electrons from 2 to 1200 eV. After each explosion, the particle instruments recorded the passage of a burst of material past the spacecraft. Analysis of mass-dependent effects, plasma β, and critical ionization velocity parameters are presented, together with a comparison to earlier experimental observations. In particular we note that the duration of the enhanced ion fluxes is controlled by the jet velocity and drops sharply when the jet velocity falls below the critical ionization velocity for each ion, with the peak ion fluxes only observed while v j e t > V c r i t (O+).