Plasma Blob Events Observed by KOMPSAT-1 and DMSP F15 in the Low Latitude Nighttime Upper Ionosphere

Here we report the plasma blob events (plasma density enhancements) that were observed from KOMPSAT-1 (685-km altitude, 2250 LT) and from DMSP F15 (840-km altitude, 2130 LT) in the low-latitude F region. The blobs were observed mostly along the +/-15^o magnetic latitudes. Their global distribution showed a season-longitudinal dependence similar to the distribution of the equatorial plasma bubbles. The blobs drifted upward relative to the ambient plasmas, and the electron temperatures and H⁺ proportions were lower within the blobs compared to those in the background. Those characteristics of the plasma blobs show close similarity to the characteristics of the equatorial plasma bubbles. Therefore, it is suggested that the blobs were originated from the lower altitudes by the mechanism that drives an upward drift of the plasma bubbles. The blob events did not occur in a correlated way with the magnetic activity or daily variation of the solar activity.