In situ active experiment techniques to study the ionosphere

In situ active experiment techniques can be used to study the natural ionosphere, to simulate natural or artificial ionospheric disturbances, and to provide a test bed for radiowave propagation studies. The opportunity for remote optical diagnostics and a relatively short ionization time in full sunlight make barium the most popular ion-producing in situ experiment material. Active observation experiments for tracing plasma irregularities are discussed, taking into account the Periquito Dos experiment and the Chemically Active Material Ejected from Orbit (CAMEO) experiment. The Periquito Dos experiment utilized barium ions to trace out the 'throat' convection pattern in the low-altitude dayside magnetospheric cusp region. The CAMEO experiment involved thermite barium releases from a satellite at 965-km altitude over the polar cap. The simulation of ionospheric disturbances is also considered along with a topside auroral ionosphere modification experiment.