Plasma blobs and irregularities concurrently observed by ROCSAT‐1 and Equatorial Atmosphere Radar

Abstract

Plasma density enhancements, or plasma blobs, and radar backscatter plumes in the nighttime equatorial F region, both of which are intriguing phenomena associated with equatorial spread F (ESF), were concurrently observed for the first time on 8 March 2004 along a common magnetic flux tube. The observational results are strong evidence of a close relationship between plasma bubbles and blobs in the equatorial ionosphere. Plasma blobs were detected by Republic of China Scientific Satellite (ROCSAT)‐1 at a dip latitude of ∼9°N, while the 47‐MHz Equatorial Atmosphere Radar (EAR) in Sumatra, Indonesia, observed the backscatter plume associated with plasma density depletions, or plasma bubbles, at dip latitudes of as high as 13°S. The plumes grew upward with large Doppler velocity away from the radar late in the premidnight sector, in association with the appearance of the plasma blobs. The zonal structure and upward drift velocity of the blobs correspond to those of the plumes on the common magnetic flux tube. Localized eastward polarization electric fields probably play an important role in the generation of plasma blobs as well as the resurgence of the plumes.