A quasi‐local theory of the E × B instability in the ionosphere

It is found that a new transient wave mode, which will be termed the “quasi‐local mode”, is associated with the E × B instability in the presence of a velocity shear. This quasi‐local wave mode is different from the nonlocal and the local eigenmodes, both of which have been studied extensively. The quasi‐local mode has the following novel properties: (1) the quasi‐local mode evolves from the local wave mode; (2) the wave number of the quasi‐local mode increases with time; and (3) the wave mode grows, reaches a saturation level, then decays due to the increase of wave number. This mode may be responsible for the observed short wavelength turbulence (i.e., λ < 1 km) in the E and F regions of the ionosphere in the presence of strong velocity shear.