Freja observations of multiple injection events in cusp

The TICS (Three‐dimensional Ion Composition Spectrometer) instrument on board the Freja satellite provides particle data with high spatial, temporal, spectral, and mass resolution. The Freja orbit (inclination 63°) is suitable for studies of the cusp since the satellite traverses this region longitudinally when the cusp is located lower than 75° geomagnetic latitude, i.e. when the interplanetary magnetic field (IMF) points southward. The satellite traverses the dayside polar region during two weeks every 100 days due to orbit precession, and nearly 50 cusp traversals were recorded during the first year of operation. Both multiple injections and single injections are clearly identified and distinguished, the former being more frequently observed than the latter. Freja has also resolved overlapping injections (special cases of multiple injections), for the first time at low altitudes.