Study of the variation of the thermosphere by equatorial atmospheric energy

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We have been conducted ground-based observations of the ionosphere and thermosphere in Indonesia, Japan, and Australia We paid special attention to 100-1000 km scale disturbances in the equatorial F-region ionosphere and thermosphere, i.e., medium-scale traveling ionospheric disturbances (MSTIDs) and plasma bubbles. MSTIDs detected with a 630-nm all-sky imager at Kototabang in Indonesia appear within and in the south of the equatorial F-region anomaly crest with a high occurrence in May and June, and have, on the average, a phase velocity of 300 m/s toward the south and a wavelength of 700 km. Plasma bubbles moving eastward at about 100 m/s have a scale of about 100 km with spacings of 200-250 km, and are embedded within plasma structures with an east-west scale of about 1000 km. MSTIDs and giant plasma bubbles can be simultaneously detected at lower midlatitudes in Japan and Australia that are connected by the geomagnetic field line, and are very identical in appearance in the both hemispheres. Equatorial ionospheric scintillations of GPS radio waves associated with plasma bubbles have been continuously monitored at Kototabang. They appear predominantly from sunset to midnight in equinoctial months, a characteristic of equatorial plasma bubble occurrences. To investigate possible dynamical coupling between the ionosphere/thermosphere and troposphere over the equator, we compare the scintillation activity and Earth's brightness temperature (Tbb) variation over the Indian Ocean. The results indicate the following: 1) the scintillation occurrence and Tbb variation are modulated by planetary waves with periods from a few days to several tens of days, and 2) the scintillation tend to be enhanced when high and low Tbb regions appear in the west of Kototabang, suggesting that plasma bubbles may be seeded by atmospheric gravity waves propagating upward from the troposphere.