Propagation characteristics of nighttime mesospheric and thermospheric waves observed by optical mesosphere thermosphere imagers at middle and low latitudes

Abstract

We review measurements of nighttime atmospheric/ionospheric waves in the upper atmosphere in Japan, Indonesia, and Australia, using all-sky airglow imagers of optical mesosphere thermosphere imagers (OMTIs). The imagers observe two-dimensional patterns of airglow emissions from oxygen (wavelength: 557.7 nm) and hydroxyl (OH) (near-infrared band) in the mesopause region (80-100 km) and from oxygen (630.0 nm) in the thermosphere/ionosphere (200-300 km). Several statistical studies were done to investigate propagation characteristics of small-scale (less than 100 km) gravity waves in the mesopause region and medium-scale traveling ionospheric disturbances (MSTIDs, ∼100-1,000 km) in the thermosphere/ionosphere. Clear seasonal variations of occurrence and propagation directions were reported for these waves. The propagation directions in the mesopause region are controlled by wind filtering, ducting processes and relative location to the wave sources in the troposphere. Poleward-propagating waves tend to be observed in the summer in the mesopause region at several stations, suggesting that mesospheric gravity waves are generated by intense convective activity in the equatorial troposphere. On the other hand, systematic equatorward and westward motions were observed for all seasons for nighttime MSTIDs in the midlatitude ionosphere with geomagnetic conjugacy between the northern and southern hemispheres. Ionospheric instabilities may play important role for the generation and propagation of these MSTIDs. We also give an example of simultaneous observation of quasi-periodic southward-moving waves in the mesopause region and in the thermosphere at the geographic equator. From these results, we discuss mean wind acceleration by mesospheric gravity waves and penetration of gravity waves from the mesosphere to the thermosphere.

Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

“…Recently, MSTIDs have been studied statistically in many places worldwide using various techniques (Frissell et al 2014(Frissell et al , 2016Fukushima et al 2012;Grocott et al 2013;He et al 2004;Ichihara et al 2013;Ishida et al 2008;Klausner et al 2009;Kotake and Otsuka 2007;Medvedev et al 2013;Oinats et al 2015Oinats et al , 2016Otsuka et al 2011Otsuka et al , 2013Shiokawa et al 2003Shiokawa et al , 2009. In this study, we present observations of MSTIDs' horizontal velocities over Taiwan using HF Doppler sounding.…”

Lower-thermospheric wind fluctuations measured with an FPI during pulsating aurora at Tromsø, Norway

“…A new all-sky camera (ASC, camera #12 of the Optical Mesosphere Thermosphere Imagers (OMTIs); Shiokawa et al, 2009) was also installed at the Tromsø EISCAT radar site. This camera includes a filter wheel used to select one of the six optical filters (channel 1: 557.7 nm, channel 2: 630.0 nm, channel 3: OH band (720 ∼ 1000 nm), channel 4: 589.3 nm, channel 5: 572.5 nm, and channel 6: 732.0 nm).…”

Joint observations of a traveling ionospheric disturbance with the Paratunka OMTI camera and the Hokkaido HF radar

“…Over the last decade, several airglow cameras, Optical Mesosphere Thermosphere Imagers (OMTIs), were installed by the Nagoya University at various locations (Shiokawa et al, 2009) as a part of a general effort to study global scale phenomena such as gravity wave generation, their propagation and effects in various atmospheric and ionospheric regions. In this study we consider data from an OMTI camera installed on the Russian territory at Paratunka, Kamchatka, (52.97 N, 158.25 E, dipole magnetic latitude: 45.8 N), Fig.…”