Wave characteristics of geomagnetic pulsations across the dip equator

In order to clarify the wave characteristics of Pi2 and Pc 4-5 magnetic pulsations around the dip equator, we analyzed magnetic data from the latitudinally dense magnetometer array in Brazil. We found that the phase difference between Pi2 pulsations observed at globally separated low-latitude stations is small, whereas Pi2 pulsations observed within the dayside dip equator region of ±2° latitude show phase lags of about 30° ∼ 50° behind those in the off-dip equator region. Pc 4-5 magnetic pulsations at the dip equator also show the same phase character. Pi2 amplitudes are enhanced in the equatorial region, where the phase lags of pulsations must be associated with the enhancement of ionospheric conductivity. The equatorial phase lags can be explained by invoking the induction effect of the equatorial enhanced ionospheric current above the good conductor Earth.