Spaced transmitter measurements of medium scale traveling ionospheric disturbances near the equator



[1] The motion of Medium Scale Traveling Ionospheric Disturbances (MSTIDs) was measured for 1 year from the eastern tip of Brazil, about 10° degrees south of the magnetic and geographic equators using spaced fixed frequency radio transmitters. The motion was very similar during all of the year. The daytime average direction was towards 150° azimuth (clockwise from north) and speed was typically in the range 150–300 m/s. The azimuth varied only slightly during the day being slightly more easterly during evening-morning hours. During winter months there were also some TIDs whose motion was northward. None of the known sources for MSTIDs fits well with MSTIDs having these velocity patterns. A possible unconfirmed source is the Inter-Tropical Convergence Zone (ITCZ).