Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa33b1771z&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SA33B-1771
Astronomy and Astrophysics
Astrophysics
[0328] Atmospheric Composition And Structure / Exosphere, [0358] Atmospheric Composition And Structure / Thermosphere: Energy Deposition, [7538] Solar Physics, Astrophysics, And Astronomy / Solar Irradiance, [7549] Solar Physics, Astrophysics, And Astronomy / Ultraviolet Emissions
Scientific paper
Incoherent scatter radar experiments at Millstone Hill for a consecutive 30 days have been conducted in October 2002, enabling this study of the day-to-day thermospheric variability in exospheric temperature Tex. This day-to-day variability is seen as variations at fixed local times as well as those in the tidal decompositions. Solar EUV and magnetic activity influences as the main driving factors on the day-to-day variability are investigated quantitatively. The solar EUV flux is from the TIMED/SEE space weather product, allowing for detailed studies of the EUV-Tex correlation, EUV band dependency and time delay of thermospheric responses. Main findings include, (1) to precisely understand thermospheric temperature day-to-day variability, the daily F107 data is typically insufficient and the EUV data is essential. (2) There is a 20--60-hour time delay in the Tex response to solar EUV flux, being short in the morning and long in the afternoon and at night. (3) Tex is most sensitive, with an approximately 2-day delay, to the EUV flux at wavelengths of 27--34 nm and 30.4 nm. A model including only the EUV flux at 27--34 nm with a 2-day time delay can generate 90% of the observed variability in the diurnal DC component. Tex is relatively less sensitive to the flux at 133.5 nm and 145--165 nm. (4) With a two-day time delay, the flux at 0.1--7 nm band is clearly positively correlated to the diurnal amplitude, and negatively correlated to the semidiurnal amplitude. (5) Magnetic activity control, as represented by the Dst index, tends to be weaker during the day and stronger at night, and is, in all three tidal components examined (DC, diurnal and semidiurnal amplitudes), most important for the semidiurnal amplitude and least important for the DC component.
Erickson Phil J.
Holt John M.
Woods Thomas N.
Zhang Sheng
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