Detection of three distinct regions in the equatorial electrojet in the Brazilian sector

Abstract

We carried out an equatorial electrojet campaign in December 1999, using the RESCO coherent backscatter radar at São Luís, at the geomagnetic equator. In this paper we selected the period from December 11 through December 19, which covers both relatively disturbed and quiet days. For this period 16 spectrograms were obtained for each day of observation with each spectrogram corresponding to one range gate. The first gate corresponds to 97.4-km height while the last gate corresponds to 115.6-km and they were sampled at 2.6-km intervals. Daily Range Time Intensity maps were generated for this period. Through the analysis of the spectrograms and considering the enhancements in the equatorial electrojet observed in the evening of some days, it was possible to observe three distinct regions as identified earlier by Pfaff and others (1987) and Kudeki and others (1987). Indeed, our observations agree with the Condor Equatorial Electrojet Campaign results. We have used the auroral activity indexes AU and AL as well as the equatorial ring current index D to evaluate the response of the equatorial electrojet to magnetic disturbances.