1ST INCOHERENT-SCATTER MEASUREMENTS OF THE EQUATORIAL-E LAYER OBTAINED WITH THE ALTAIR RADAR

We describe the first incoherent-scatter (IS) radar measurements made of the daytime E layer at equatorial latitudes. Using ALTAIR, a steera ble IS radar located in the Kwajalein Atoll, we not only show that the E-layer profiles are consistent with those obtained in situ by rocket s, we present the first direct evidence of a latitudinal gradient in p lasma density in the bottomside E layer that extended from 3-degrees N dip latitude to beyond 6-degrees N. We suggest that the gradient invo lves the electrodynamic transport of metallic ions, e.g., the gradient could be produced by the equatorial metallic-ion fountain or possibly by the dumping of metallic ions at the base of the E layer by the win d-shear mechanism for sporadic E. We close with a brief discussion of the implications of such a gradient on the equatorial electrojet.