HR: 0800h
AN: SA21A-0279    [Abstracts]
TI: ROCSAT Observations of Meso-Scale Density and Flow Undulations in Conjuction with Intermediate-Scale Density Irregularities at Midlatitude Topside Ionosphere
AU: * Su, S
EM: sysu@jupiter.ss.ncu.edu.tw
AF: National Central University, 300 Chung-Da Rd., Chung-Li, TWN 32000 Taiwan
AU: Tsunoda, R T
EM: tsunoda@sri.com
AF: SRI International, Menlo Park, Menlo Park, CA 90900 United States
AU: Liu, C
EM: liu@cc.ncu.edu.tw
AF: National Central University, 300 Chung-Da Rd., Chung-Li, TWN 32000 Taiwan
AU: Chao, C
EM: ckchao@jupiter.ss.ncu.edu.tw
AF: National Central University, 300 Chung-Da Rd., Chung-Li, TWN 32000 Taiwan
AU: Wu, J
EM: jmwu@csrsddc.csrsr.ncu.edu.tw
AF: National Central University, 300 Chung-Da Rd., Chung-Li, TWN 32000 Taiwan
AU: Ho, H
EM: hhho@csrsddc.csrsr.ncu.edu.tw
AF: National Central University, 300 Chung-Da Rd., Chung-Li, TWN 32000 Taiwan
AB: ROCSAT-1 orbiting at 600 km topside ionosphere frequently observes the meso-scale (~50 to 1000 km) ion density and flow undulations at low- to mid-latitudes. During the 8 January 2000 event, noticeable intermediate-scale (1 to 50 km) density irregularities were also observed at midlatitude in conjunction with the meso-scale undulations in many consecutive ROCSAT orbits. The meso-scale density and flow undulations indicate in-phase variations among the radial outward flow, westward flow, and the density enhancement. During these consecutive ROCSAT orbits of observing the meso-scale undulations, the calculated electric field perturbations all point to the northeast-southwest direction at about ° in azimuth. This implies that a frontal structure of the meso-scale disturbance is aligned from northwest to southeast in geographic coordinate. The in-phase undulations of the flow and density variations together with the tilted frontal structure for the meso-scale disturbance fit the predicting result of the Perkins instability [Perkins, 1973]. It could also be caused by the disturbances mapped from plasma cloud instabilities in E region in the model of Hysell et al. [2002] or from the instabilities in the sporadic E layers proposed by Haldoupis et al. [2003] and Tsunoda et al. [2004]. As for the intermediate-scale density irregularities, no correlated phase relationship is found between the density fluctuations and the flow variations. From the fact that the occurrences of the intermediate-scale irregularities are isolated from the meso-scale undulations, we conclude that the cause of the intermediate-scale irregularities should be different from what triggered the meso-scale undulations. The possible interaction between the two triggering mechanisms for the irregularities of the two different scales will be discussed.
DE: 2437 Ionospheric dynamics
DE: 2439 Ionospheric irregularities
DE: 2443 Midlatitude ionosphere
DE: 2481 Topside ionosphere
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005