HR: 0800h
AN: SA21A-03    [Abstracts]
TI: VHF Radar Observations of Nighttime F-Region Field-Aligned Irregularities Over Kototabang, Indonesia
AU: * Otsuka, Y
EM: otsuka@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: Shiokawa, K
EM: shiokawa@stelab.nagoya-u.ac.jp
AF: Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
AU: Ogawa, T
EM: taogawa@nict.go.jp
AF: National Institute of Information and Communications Technology, 4-2-1 Nukui- Kitamachi, Koganei, Tokyo, 184-8795, Japan
AU: Drs, E
EM: fendy@idola.net.id
AF: National Institute for Aeronautics and Space, Bandung, Indonesia
AB: We report continuous observations of the nighttime F-region field-aligned irregularities (FAIs) over Indonesia. A VHF radar with operating frequency of 30.8 MHz and peak power of 20 kW has been operated at Kototabang (0.20°S, 100.32°E; dip latitude 10.4°S), Indonesia since February 2006. Five beams were allocated between ±54° in azimuth around geographic south (126°-234°). From the continuous observation from February 2006 to November 2007, we found that FAIs appeared frequently at pre- midnight between March and May and at post-midnight between May and August. The pre-midnight FAIs coincided well with GPS scintillation observed at the same site. Seasonal and local time variations of the pre-midnight FAI occurrence are consistent with those of equatorial plasma bubbles reported in previous studies (e.g., Maruyama and Matuura, 1984). These results indicate that the pre-midnight FAIs could be associated with the equatorial plasma bubbles. On the other hand, seasonal and local time variations of the post-midnight FAIs were inconsistent with those of the plasma bubbles. The features of the post-midnight FAIs can be summarized as follows: (1) The post-midnight FAIs are not accompanied by GPS scintillations. (2) Most of the post-midnight FAI regions do not show propagation, but some of them propagate westward. (3) Echo intensity of the post-midnight FAIs was weaker than that of the pre-midnight FAIs. These features are similar to those of the FAI echoes that have been observed at mid- latitude (e.g., Fukao et al., 1991). At Kototabang, Fukao et al. (2004) have firstly observed FAIs that resemble those at mid-latitude. The present paper reports statistical characteristics of the mid-latitude-type FAIs observed at Kototabang.
DE: 2415 Equatorial ionosphere
DE: 2435 Ionospheric disturbances
DE: 2437 Ionospheric dynamics
DE: 2439 Ionospheric irregularities
DE: 6952 Radar atmospheric physics (1220)
SC: SPA: Aeronomy [SA]
MN: 2009 Joint Assembly