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Volume 61 Supplement 4

Special Issue: Coupling Processes in the Equatorial Atmosphere (CPEA)

VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia

Earth, Planets and Space volume 61, pages 431–437 (2009)Cite this article

Abstract

We report, for the first time, 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.

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Author notes

  1. T. Ogawa

    Present address: National Institute of Information and Communications Technology, Tokyo, Japan

Authors and Affiliations

  1. Solar-Terrestrial Environment Laboratory, Nagoya University, Japan

    Y. Otsuka & T. Ogawa

  2. National Institute for Aeronautics and Space, Bandung, Indonesia

    Effendy

Authors
  1. Y. Otsuka
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  2. T. Ogawa
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  3. Effendy
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Correspondence to Y. Otsuka.

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Otsuka, Y., Ogawa, T. & Effendy VHF radar observations of nighttime F-region field-aligned irregularities over Kototabang, Indonesia. Earth Planet Sp 61, 431–437 (2009). https://doi.org/10.1186/BF03353159

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