Plasma waves and transversely accelerated ions in the terrestrial ionosphere

Developments in measuring the physical mechanisms responsible for strongly driven transverse ion acceleration in the ionosphere are reviewed. Lower-hybrid waves and ion Bernstein waves can be associated very closely with transversely accelerated ions in the auroral ionosphere. In a recent development, very intense and localized lower-hybrid waves have been observed to produce transversely accelerated ions with characteristic energies of 10 eV. The case for current-driven electrostatic oxygen cyclotron waves producing transversely accelerated ions is less compelling.