On the role of horizontal wind shears in the generation of F0.5 layers over the dip equatorial location of Thiruvananthapuram: A numerical simulation study

A numerical simulation is carried out to estimate the rate of convergence of ionization required to produce a F0.5 layer with peak plasma frequency (foF0.5) of 3.2 MHz from three different background layer densities, over Thiruvananthapuram (8.5°N; 77°E; dip latitude ~ 0.5°N), a dip equatorial station in India. Further the simulation study is extended to understand the convergences required by considering the seasonal mean peak F0.5 layer frequencies also. One possible mechanism by which this convergence can be produced is by a horizontal shear in the meridional wind. The corresponding shears required to generate the layer with the above convergence conditions are estimated. It is found that gravity waves are capable of generating wind shears, leading to the pooling of ionization and the generation of the layer over the dip equator. A meridional wind with the gravity wave induced wind shear is numerically estimated. Finally, the short scale gravity waves of periods around 3-23 min have been inferred to be more efficient in generating the wind shear when compared to large scale horizontal waves leading to the generation of F0.5 layer.