Some characteristics of the ionospheric irregularities associated with Esq layers


  • H. Chandra,

  • R. G. Rastogi


Spaced fading records at Thumba for times when Esq disappears following large changes in the geomagnetic H component are studied. The results for the periods when Esq is present are known to show fast fading, westward drift, and highly elongated ground diffraction patterns with a small semiminor axis. During periods when there is no Esq the fadings are found to be very slow, the drift direction is reversed to the east, and the ground diffraction pattern becomes almost isotropic with a large semiminor axis, whose alignment is a few degrees off the magnetic N-S direction. The characteristics of the fading and those of the ground diffraction pattern when Esq disappears are similar to the characteristics usually obtained at latitudes well away from the equator. The Esq is thus suggested to be a superposition of additional irregularities over the normal E region irregularities (similar to those in the E region at nonequatorial latitudes). Close dependence of the direction of the electric field with the occurrence of Esq favors the conclusion that Esq is due to the cross-field instability created by the action of the H field with the Hall polarization field and the plasma density gradient.