Observation of lithium pick‐up ions in the 5‐ to 20‐keV energy range following the Ampte solar wind releases

Newly created 5‐ to 20‐keV lithium ions were observed for limited time periods following the first Active Magnetospheric Particle Tracer Explorers (AMPTE) lithium release in the solar wind on September 11, 1984. The detection of these so‐called “pick‐up” ions by the time‐of‐flight spectrometer SULEICA (suprathermal energy ionic charge analyzer) on the AMPTE/IRM satellite depends critically on the orientation of the interplanetary magnetic field with respect to the directions of the solar wind and the spin axis of the IRM spacecraft, which was favorable only during the short time when these ions were seen. Our observations are compatible with a shell‐like expansion of the Li cloud with velocities of about 2.5 km/s. The signatures by which the artificial pick‐up ions are identified can also be used to detect and investigate natural pick‐up ions.