On Seeding, Large-Scale Wave Structure, Equatorial Spread F, and Scintillations Over Vietnam


Tsunoda, R. T., Yamamoto, M., Tsugawa, T., Hoang, T. L., Tulasi Ram, S., Thampi, S. V., … & Nagatsuma, T. (2011). On seeding, large‐scale wave structure, equatorial spread F, and scintillations over Vietnam. Geophysical Research Letters, 38(20).


Understanding the day-to-day variability in occurrence of equatorial spread F (ESF) remains as a high-priority objective in space weather research. A major difficulty has been an inability to resolve the roles being played by large-scale wave structure (LSWS) and the post-sunset rise (PSSR) of the equatorial F layer, in the production of ESF. In this paper, we show conclusively that total electron content (TEC), measured as a function of latitude and longitude, provides clear, routine descriptions of LSWS. Then, together with ionosonde data, we show, for the first time, that while a seed for LSWS can occur in the late afternoon, its amplification takes place mostly during the PSSR. Implications of these findings are discussed in light of existing theories.

Key Points:

  • Satellite TEC measurements can be used to describe LSWS
  • LSWS is seeded in the late afternoon, not evening
  • Seeding and LSWS development is patchy and variable, not uniform and steady

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