Recent observations of traveling ionospheric disturbances and plasma bubbles using Optical Mesosphere Thermosphere Imagers in Asian and African sectors
Abstract
We review recent observational results of medium-scale traveling ionospheric disturbances (MSTIDs) and equatorial plasma bubbles obtained by using airglow imagers and Fabry-Perot interferometers of the Optical Mesosphere Thermosphere Imagers (OMTIs) at Asian and African sectors. The OMTIs contains 20 airglow imagers and 5 Fabry-Perot interferometers (FPIs) at Canada, USA (Alaska), Russia, Finland, Norway, Iceland, Japan, Thailand, Indonesia, Australia, and Nigeria (http://stdb2.isee.nagoya-u.ac.jp/omti/). The 3-dimentional Fast Fourier Transformation of airglow images makes it possible to analyze 16-year airglow images obtained at Shigaraki (34.8N) and Rikubetsu (43.5N), Japan, to obtain phase velocity spectra of gravity waves and MSTIDs. The MSTIDs spectra show clear southwestward preference of propagation and minor northeastward propagation over Japan. We also found clear negative correlation between MSTID power and solar F10.7 flux, indicating that MSTIDs becomes more active during solar quiet time. This fact suggest the control of ionospheric Perkins and E-F coupling instabilities by solar activities. Three TIDs in airglow images over Indonesia, including midnight brightness waves (MBWs), were compared with CHAMP-satellite overpass to investigate neutral density variations in the thermosphere associated with the TIDs. We found clear correspondence in variations between the airglow intensities and neutral densities, suggesting that the observed TIDs over the equatorial region is caused by gravity waves. We also compare average thermospheric temperatures measured by the four FPIs for 3-4 years with the MSIS90E and GAIA models. The comparison shows that GAIA generally shows better fitting than the MSIS90E, but at the equatorial stations, GAIA tends to fail to reproduce the FPI temperature, probably due to ambiguity of location of the midnight temperature maximum. We also made statistics of plasma bubble occurrence using airglow imager and GNSS receiver at Abuja (9.0N), Nigeria near the geomagnetic equator based on 1.6 year observations. The bubble occurrence is high at equinoxes. There are 33 % of events for which bubble detection by airglow image and GNSS ROTI is different. We discuss possible cause of these differences in the presentation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMSA12A..03S
- Keywords:
-
- 2415 Equatorial ionosphere;
- IONOSPHERE;
- 2435 Ionospheric disturbances;
- IONOSPHERE;
- 2437 Ionospheric dynamics;
- IONOSPHERE;
- 2443 Midlatitude ionosphere;
- IONOSPHERE