Ion‐ion kink instability in the magnetotail: 1. Linear theory

A number of different ion species are known to exist in the magnetotail. In particular, cold lobe ions and current‐carrying hot plasma sheet ions are a permanent feature of the magnetotail and result in various types of instabilities. One such instability is the ion‐ion kink mode. Detailed properties of this mode in the magnetotail are investigated in a two series paper using a combination of linear Vlasov theory, three‐dimensional (3‐D) full particle and hybrid (fluid electron, kinetic ions) simulations. Here we consider the linear properties of the mode in detail. Although the mode shows similarities to a velocity driven instability, its linear mode properties do exhibit dependencies on the kinetic details of the secondary ion population.