In the absense of reconnection , magnetopause and cross-tail current are also tangential discontinuities. Of the shocks, fast shocks are the most typical in solar system plasmas. For example, Earth's bow shock is a fast shock, as are also most interplanetary shocks in the solar wind. An important factor influencing the shock behaviour is the shock geometry, i.e., direction of the upstream magnetic field. It is measured using an angle T between the field and the shock normal.
Oblique shock is something in between.
Shock strength tells the amount of energy processed by the shock. It is measured with the Mach number. Higher Mach number shocks are called supercritical as opposed to subcritical shocks. In all shock formations there is, by definition, irreversible dissipation that transforms the ram energy of the plasma flow into thermal energy. The waves grow due to some instability, which will be driven by departure from equilibrium of the particle distribution function.