HR: 0800h
AN: SA21A-0272    [Abstracts]
TI: Effects of neutral compositions on the ionospheric positive storms during the recovery phase
AU: * Lei, J
EM: leijh@mail.igcas.ac.cn
AF: NCAR High Altitude Observatory, P.O. Box 3000, Boulder, CO 80307 United States
AU: Zhang, S
EM: shunrong@haystack.mit.edu
AF: MIT Haystack Observatory, Off Route 40, Westford, MA 01886 United States
AU: Zhang, Y
EM: yongliang.zhang@jhuapl.edu
AF: JHU Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AB: The ionosonde measurements over Millstone Hill (42.6°N, 71.5°W), Wallops Is (37.9°N, 75.5°W), Eglin Afb (30.4°N, 86.7°W) and Boulder (40°N, 105.3°W) along with simultaneous GUVI/TIMED [O]/[N2] density ratio measurements are analyzed to investigate positive storm effects during the recovery phase of the April 2004 magnetic storm. The results show that the peak density NmF2 increases significantly on 4 April, 2004 (the recovery phase) with respect to the quiet reference days, especially over Boulder. It is generally accepted that the daytime positive storm results from dynamic processes (the neutral winds/electric field effects) that lift the F2 layer, decreases the recombination rate, and increases the electron density. However, this can't explain these observed phenomena on 4 April, where hmF2 doesn't present evident changes during this period. In fact during this period we find an evident increase in the simultaneous TIMED/GUVI [O]/[N2] density ratio. We suggest that the thermospheric composition perturbation should contribute largely to the ionospheric positive storms at middle latitudes during the recovery phase of the April 2004 storm.
DE: 2419 Ion chemistry and composition (0335)
DE: 2437 Ionospheric dynamics
DE: 2441 Ionospheric storms (7949)
DE: 2443 Midlatitude ionosphere
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005