Publication Date:
2015-04-04
Description:
Thermospheric densities observed by CHAMP and GRACE satellites during 2002–2010 and the globally averaged thermospheric densities from 1967 to 2007 have been used to investigate latitudinal, longitudinal, and height dependences of the multi-day oscillations of thermospheric densities. The data show that the main multi-day oscillations in thermospheric densities are 27-, 13.5-, 9-, and 7-day oscillations. The high correlation coefficients between the density oscillations and the F 10.7 or Ap index indicate that these oscillations are externally driven. The 27-day density oscillation, being the strongest, is induced by variations in solar radiation, as well as recurrent geomagnetic activity that is the result of corotating interaction regions (CIRs) and high-speed solar wind streams of coronal hole origin. Density oscillations at periods of 13.5, 9, and 7 days at solar minimum and during the declining phase are stronger than those at solar maximum. These oscillations are mainly associated with recurrent geomagnetic activity due to coronal hole high speed streams and CIRs. The multi-day, periodic oscillations of thermospheric density exhibit strong latitudinal and longitudinal variations in the geomagnetic coordinate and oscillate synchronously at different heights. Oscillations with zonal wavenumber zero oscillate globally, whereas those with nonzero wavenumbers are strong at high geomagnetic latitudes, and hemispherically asymmetric. They are stronger in the south hemisphere. The spectral distributions of thermospheric densities at different heights have almost the same latitude and longitude structures, but the spectral magnitudes increase with height.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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