Earth Planets Space, Vol. 56 (No. 7), pp. e21-e24, 2004E-LETTER
Jyunpei Uemoto, Takayuki Ono, Atsushi Kumamoto, and Masahide Iizima
Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
(Received June 6, 2004; Revised July 20, 2004; Accepted July 20, 2004)
To verify an additional ionization layer predicted in the equatorial ionosphere, topside ionograms obtained by the Planetary Plasma Sounder (PPS) system on-board the Ohzora (EXOS-C) satellite were analyzed. Based on the analysis of the PPS data of 8 passes in March and 11 passes in May, 1987, the ionization ledge observed in the local noon time period shows similar nature as it has been theoretically predicted for the F3 layer by Balan and Bailey (1995). It was noted that some peaks of the ledge structure were located on the field line of higher latitude region than the field line of the crest of the equatorial anomaly.
Key words: Equatorial ionosphere, topside sounder, Ohzora (EXOS-C) satellite, F3 layer, ionization ledge.