ORCID Profile
0000-0002-3876-2946
Current Organisations
National Institute of Polar Research
,
Kyoto University
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Publisher: Elsevier BV
Date: 2004
Publisher: Elsevier BV
Date: 05-2002
Publisher: Elsevier BV
Date: 05-2002
Publisher: Elsevier BV
Date: 05-2002
Publisher: American Geophysical Union (AGU)
Date: 08-2023
DOI: 10.1029/2022JA030769
Abstract: Atmospheric gravity waves (AGWs) and medium‐scale traveling ionospheric disturbances (MSTIDs) in the upper atmosphere can be observed in nocturnal airglow images. Spectral analysis of airglow images provides propagation direction and intensity of these waves. However, the spectral analysis of airglow images has not been done yet for stations in the southern hemisphere except for Antarctica. In this study, we calculated the horizontal phase velocity spectra of AGWs in the mesosphere‐lower‐thermosphere (MLT) region near the mesopause and MSTIDs in the F‐region ionosphere from airglow images at wavelengths of 557.7 and 630.0 nm, respectively, by applying the 3‐dimensional Fourier spectral analysis to the airglow images obtained at Darwin (12.4°S, 131.0°E) in Australia for 13.75 years from 2001 to 2007 and from 2011 to 2019. The spectra of AGWs in the MLT region show clear characteristics that the southward power spectral density (PSD) is stronger in summer and weaker in winter. Tropospheric convection was located at north of Darwin in summer and above Darwin in winter, suggesting that the tropospheric convection is a possible source of AGWs in the mesopause region. The spectra of MSTIDs in the F‐region ionosphere show that the dominant northwestward PSD is stronger in winter and during solar quiet periods. These features can be explained if the observed MSTIDs are caused by the ionospheric instabilities. A weak positive correlation was observed between PSDs of AGWs in the mesosphere and MSTIDs. We propose that the MSTIDs propagating other than northwestward may be generated by AGWs.
Publisher: American Geophysical Union (AGU)
Date: 09-2017
DOI: 10.1002/2016JD026217
Publisher: Elsevier BV
Date: 1999
Publisher: American Geophysical Union (AGU)
Date: 10-2004
DOI: 10.1029/2003RS003026
Publisher: American Geophysical Union (AGU)
Date: 06-11-2004
DOI: 10.1029/2003JD003378
No related grants have been discovered for Takuji Nakamura.