Onset Condition of Plasma Density Enhancements: A Case Study for the Effects of Meridional Wind During 17-18 August 2003

The multisatellite observations were used to study the possible factors leading to the development of the plasma density enhancements during the August 2003 storm period. The plasma depletions and enhancements (also referred as bubbles and blobs, respectively) were observed by first satellite of the Republic of China around 345 degrees E sector at different local time on 17 August, before the midnight after the storm sudden commencement. However, only the depletions were recorded on 18 August at the same longitude sector and at nearly the same time as that on 17 August. The motions of the bubbles and blobs displayed different characteristics on 17 August. From Challenging Mini-satellite Payload, Gravity Recovery and Climate Experiment, and total electron content map, the equatorial ionization anomaly was inhibited and displayed more asymmetric on 17 August and became stronger on 18 August. A density enhancement near the northern crest was recorded by Gravity Recovery and Climate Experiment, and similar enhancements were found in total electron content map at low-latitude regions of both hemispheres on 17 August. The results suggest that the meridional neutral wind is crucial and plays an important role in the development of the plasma blobs. And the variations of meridional neutral wind may be linked with the large-scale traveling ionospheric disturbances during the disturbed periods.