Multi-day Periodicities in Thermosphere Density during the Declining Phase of Solar Cycle 23 Jiuhou Lei,Jeffrey P. Thayer, Jeffrey M. Forbes, Eric K. Sutton, and R. Steven Nerem Department of Aerospace Engineering Sciences University of Colorado
Outline 1. CHAMP Density in 2005 2. Solar Activity Dependence of Multi-day Periodicities 3. Preliminary Comparison between Data and TIEGCM
27 days/3 CHAMP density in 2005 Lei, J., J. P. Thayer, J. M. Forbes, E. K. Sutton, and R. S. Nerem (2008), Rotating solar coronal holes and periodic modulation of the upper atmosphere, Geophys. Res. Lett., 35, L10109, doi:10.1029/2008GL033875.
Thermospheric density response to solar wind: 2005-2007 ascend descend
Thermospheric density response to solar wind: 2002-2004 ascend descend
Latter part of the declining phase Solar Activity Dependence
Correlation between density oscillations and Kp Percent of the band-pass filter density residuals to 11-day running mean. The band-pass filter was centered at the period of 9 days.
Summary I • The neutral densities show the presence of several prominent periods around 9, 7, and 5 days from 2004-2007, with the most pronounced periodicities of 9 and 7 days observed in 2005, and 2006, respectively. • 2. The periodicity of neutral density highly correlates with that of geomagnetic activity and solar wind parameters during the latter part of the declining phase. This solar activity dependence of the periodicities is explained by the corresponding variations of high-speed solar wind and the associated geomagnetic activity. Lei, J., et al. (2008b), Global thermospheric density variations caused by high-speed solar wind streams during the declining phase of solar cycle 23, J. Geophys. Res., doi:10.1029/2008JA013433, in press.
Ionospheric response Lei, J., et al. (2008), Ionosphere Response to Solar Wind High-Speed Streams, Geophys. Res. Lett., doi:10.1029/2008GL035208
Summary II 9- and 7-day periodic oscillations are also present in the global mean Total Electron Content (TEC) from 1 January 2005 to 31 December 2006. Spectral analysis indicates that the pronounced periodicities of 9 and 7 days observed in TEC are associated with variations in solar wind high-speed streams and geomagnetic activity.