It is usually believed that the spatial transverse shear in the parallel flow destabilizes many low frequency oscillations and this may be the origin of low frequency oscillations in the ionosphere. Here we show that this picture can be changed altogether if one considers the flow curvature (second spatial derivative) into account. The transverse curvature in the parallel flow unlike the parallel flow shear can stabilize or destabilize the low frequency modes depending on the sign of flow curvature and on the nature of the mode.

References