Electrostatic instabilities triggered by finite amplitude Alfvén/ion-cyclotron waves and relative drifts among the ion components in the magnetosphere

Alfvén/ion‐cyclotron waves have been observed in several regions of the magnetosphere. Parametric decays of finite amplitude Alfvén/ion‐cyclotron waves in the presence of He+ ions and a mixed population of thermal and hot protons have been shown to lead to several parametric instabilities. These studies assumed that heavy ions are not drifting relative to each other. However, a relative drift velocity among the ions can affect known parametric decays and can also lead to new ones. Moreover, finite amplitude waves in a plasma system with drifting ion species are shown to destabilize nonlinear ion‐acoustic‐like waves supported by each species. Finally, linear ion‐acoustic waves supported by different ion species can also be destabilized because of the relative drift between ion components.