Ionospheric Disturbances Over Indonesia and Their Possible Association With Atmospheric Gravity Waves From the Troposphere(<Special Issue>CPEA-Coupling Processes in the Equatorial Atmosphere)

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As part of the CPEA (Coupling Processes in the Equatorial Atmosphere) project, we have been conducting ground-based optical and radio observations of the ionosphere and thermosphere at Kototabang in Indonesia, Japan, and Australia. First, this paper gives a brief overview of some results, paying special attention to 100-1000km scale plasma disturbances in the F region ionosphere, i.e., medium-scale traveling ionospheric disturbances (MSTIDs) and plasma bubbles. MSTIDs over the equator are observed within and in the south of the F region equatorial anomaly crest and have, on the average, a phase velocity of 300m s^<-1> toward the south, a period of 40min, and a wavelength of 700km. Plasma bubbles move to the east at 〜100m s^<-1>, have a scale of about 100km with spacings of 200-250km, and are embedded within plasma structures with a scale of about 1000km. Interestingly, giant plasma bubbles can be simultaneously detected at lower midlatitudes in southern and northern hemispheres that are connected by the geomagnetic field line, and are very identical in appearance in the both hemispheres. Then, we present newly-obtained characteristics of equatorial ionospheric scintillations of 1.6GHz GPS radio waves associated with plasma bubbles. Continuous scintillation observations for two years at Kototabang indicate that the scintillations appear predominantly from sunset to midnight in equinoctial months. Such a seasonal variation is also recognized from a statistical study of bubble occurrences over the Philippines, Singapore, and Indonesia. To investigate possible dynamical coupling between the ionosphere/thermosphere and troposphere over the equator, we compare the scintillation (bubble) activity and Earth's brightness temperature variation over the Indian Ocean measured by meteorological satellites. The results indicate that there can exist meaningful correlations between the scintillation occurrence and tropospheric disturbance at 80°-95°E longitudes, i.e. 5°-20°west of Kototabang. Possible processes to seed plasma bubbles are discussed.
社団法人日本気象学会の論文
2006-07-14

Ionospheric Disturbances Over Indonesia and Their Possible Association With Atmospheric Gravity Waves From the Troposphere(<Special Issue>CPEA-Coupling Processes in the Equatorial Atmosphere)

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