Japan Geoscience Union Meeting 2014

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Poster

Symbol P (Space and Planetary Sciences) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM36_28PO1] Physics and Chemistry in the Atmosphere and Ionosphere

Mon. Apr 28, 2014 6:15 PM - 7:30 PM Poster (3F)

Convener:*Otsuka Yuichi(Solar-Terrestrial Environment Laboratory, Nagoya University), Takuya Tsugawa(National Institute of Information and Communications Technology), Seiji Kawamura Seiji(National Institute of Information and Communications Technology)

6:15 PM - 7:30 PM

[PEM36-P28] Seasonal-longitudinal dependence of the occurrence of equatorial plasma bubbles obserbed by ISS-IMAP

*Akira TAKAHASHI1, Hiroyuki NAKATA1, Toshiaki TAKANO1, Akinori SAITO2 (1.Chiba University, 2.Kyoto University)

Keywords:Equatorial ionosphere, Plasma bubble, airglow, ISS-IMAP

Equatorial plasma bubbles (EPBs) are local depletions of the electron density in the ionosphere. Ionospheric irregularities are included in EPBs and cause radio signal scintillation. Recently, reseach on applying GNSS to Air Navigation System has progressed, therefore, it becomes more necessary to investigate the generation mechanism and the morphology of EPBs.In this study, we analyzed seasonal-longitudinal dependence of the occurrence of EPBs using airglow-images obtained by ISS-IMAP (Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping).In 630-nm airglow images, EPBs are visualized as black lines. 181 events are selected during 2012/09 - 2013/08. To calculate the longitudinal denpendence of occurence rate, we divide the ionosphere into 36 longitude bins, each 10 degrees wide. Since EPBs are observed at low and middle latitude, the total obserbation time is accumlated when |latitude| < 30. We calculate the occurrence rate as the number of EPBs detected over the total observation time.The occurrence rate is high at the African-Atlantic-American regeions in the equinoctial seasons. On the other hand, the occurance rate is also high at American-Pacific resions in summmer, which is not obtained in the previous study, Burke et al. [2004], in which EPBs are detected using plasma density data on DMSP satellite. The altitude of DMSP is 840 km, which is higher than the observation altitude of ISS-IMAP, that is about 250 km. Therefore, it is conceivable that the difference of occurrence rate of EPB is due to the altitude of the observations. This imply that ISS-IMAP observation could detect EPBs not developed to higher altitude.Based on above, we will present seasonal-longitudinal variability of the Rayleigh-Taylor instability growth rate, contributing the development of EPBs using ionosphere model and other observational data.