HR: 0830h
AN: SA21B-0092    [PDF]
TI: Seasonal and Latitudinal Distributions of the Dominant Light Ions at 600 km Topside Ionosphere During Years of Solar Maximum
AU: * Su, S
EM: t2700146@ncu865.ncu.edu.tw
AF: Institute of Space Science, and Center for Space and Remote Sensing Research National Central University, 300 Chung-Da Road, Chung-Li, 320 Taiwan
AU: Chao, C
EM: ckchao@jupiter.ss.edu.tw
AF: Institute of Space Science National Central University, 300 Chung-Da Road, Chung-Li, 320 Taiwan
AU: Yeh, H
EM: yeh@jupiter.ss.ncu.edu.tw
AF: Institute of Space Science National Central University, 300 Chung-Da Road, Chung-Li, 320 Taiwan
AU: Heelis, R A
EM: heelis@utdallas
AF: William B. Hanson Center for Space Sciences University of Texas at Dallas, 2601 North Floyd Road, Richardson, TX 77080 United States
AB: Data taken by ROCSAT-1 from 1999 to 2002 during years of solar maximum has been analyzed for the observations of the dominant light hydrogen or helium ions at 600 km topside ionosphere. The results reveal some interesting seasonal and latitudinal distributions of the dominant light ion species in the topside ionosphere even during years of high solar activity. The hydrogen ions are observed as the dominant ion species only during the nighttime. Except for the March spring, the distribution for such transition shows a strong hemispheric asymmetry. Furthermore, the transition that occurs in the winter hemisphere during the solstice seasons seems to be bounded along a low dip-latitude that circumscribes most of the transition occurrences in one hemisphere. No significant seasonal dependence of this latitude bound is noticed during high solar activity years. On the other hand, the occurrence of dominant helium ions is very rare but it shows the seasonal and latitudinal distributions similar to that of dominant hydrogen ions. Finally, a good correlation between the observed field-aligned ion flow and the hemispheric asymmetry for the transition of dominant hydrogen ions has been found as the cause for the asymmetry inferred from the existence of interhemispheric plasma flow in relation to the hemispheric asymmetry of the F peaks and to the enhancement or retardation of the nocturnal re-distribution of the light ions along the field line.
DE: 2419 Ion chemistry and composition (0335)
DE: 2423 Ionization mechanisms
DE: 2443 Midlatitude ionosphere
DE: 2479 Solar radiation and cosmic ray effects
DE: 2481 Topside ionosphere
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting