Some characteristics of non-two-stream irregularities in the equatorial electrojet

The analysis of VHF radar echoes from electron concentration irregularities in the equatorial electro jet indicate that there are two distinct types of irregularities in the region. One of these has previously been shown to be generated by the two-stream instability mechanism and consists of planar irregularities that travel at the ion-acoustic velocity. The other type of irregularity moves at about the electron drift velocity and can exist when the electron drift velocity is insufficient to produce the two-stream type irregularities. Drift observations of this second type of irregularity show that the electro jet current reverses during nighttime periods, the electron drift velocity being comparable to that during the day. Additional observations show that these irregularities exist in large patches that move with the same approximate velocity and retain their identity for many seconds.