Climatology of gravity waves-induced electric fields in the equatorial E region

Abstract

Equatorial electrojet (EEJ) observations using VHF radars show backscattered echoes from two types of electron density irregularities explained by the modified two-stream (Type I) and the gradient drift (Type II) instabilities. From the Type II irregularity velocities obtained by a radar installed at São Luiz Space Observatory (2.58°S, 44.23°W, magnetic latitude 0.23°S) we have inferred the vertical electric fields (E z). The Ez inference was based on geomagnetic field and atmospheric models. A harmonic analysis of these electric fields shows the presence of gravity waves (GW) induced oscillations in the EEJ. We calculated the ratio between GW-related electric fields and the total Ez, which is an indicator of the efficiency in the production of an additional electric field due to a gravity wave neutral wind. In the present paper we describe the methodology of analysis and discuss some characteristics of the gravity waves that could modify the equatorial ionospheric electric fields. Copyright 2009 by the American Geophysical Union.