  The electrostatic shear-flow-driven ion cyclotron instability of magnetic
field aligned sheared plasma flow is investigated analytically. It is shown
that the shear-flow-driven electrostatic ion cyclotron instability can be
considered as a combination of three different instabilities determined by
theirs own mechanism of excitation: ion-kinetic, ion-hydrodynamic and
electron-kinetic. Each of these instabilities are dominant in different ranges
of the wavelength along the magnetic field. The linearized dispersion equation
is solved within the limits of long and short waves along the magnetic field
where effects of electrons and ions, respectively, are dominant in the
development of these instabilities. The general criterion of instability
excitation, which couples the flow velocity shear and wave number across the
magnetic field, is obtained.
