ࡱ > x 9 R dD bjbj o Ai l F Z 4 4 b b b h ʋ d . d $ ԕ ԕ f D P R R R R R R $ v ݘ ݘ ݘ v c ԕ ԕ 7 . c c c ݘ * ԕ ԕ P c ݘ P c c M 0 T ԕ d | b K 7 $ T e H 8 T c 0WxNzz5uxsXxvz[ S e a s o n a l b e h a v i o r o f m e t e o r r a d a r w i n d s o v e r W u h a n G u a n g x i n Z h a o 1 , 2 , 3 , L i b o L i u 1 , W e i x i n g W a n 1 , B a i q i N i n g 1 , a n d J i a n g a n g X i o n g 1 1 D i v i s i o n o f G e o m a g n e t i s m a n d S p a c e P h y s i c s , I n s t i t u t e o f G e o l o g y a n d G e o p h y s i c s , C h i n e s e A c a d e m y o f S c i e n c e s , B e ijing, 100029, China 2 Wuhan Institute of Physics and Mathematics, CAS, Wuhan, 430071, China 3 Graduate School of the Chinese Academy of Sciences (Received March 23, 2004; Revised November 9, 2004; Accepted November 10, 2004) A newly installed meteor radar has been installed to measure winds in the mesosphere and lower thermosphere (MLT) over Wuhan (114.4 %E , 3 0 . 6 %N ) . I n t h e p r e s e n t s t u d y , a d a t a b a s e o f t h e f i r s t 2 5 m o n t h s ( F e b r u a r y 2 0 0 2 F e b r u a r y 2 0 0 4 ) o f o b s e r v a t i o n s h a s b e e n a n a l y z e d t o i n v e s t i g a t e t h e c l i m a t o l o g y o f m e a n w i n d s a n d t i d e s . T h e d a i l y a v e r a g e z o n a l w i n d i s c h a r a c t e r e d b y a s t r o n g s h e a r i n s o lstices and an intense eastward flow in summer. The daily average meridional wind is northward in winter and southward in other seasons. There are some discrepancies between the radar mean winds and the HWM93 model winds. The summer zonal winds and meridional winds from the model are obviously weaker than our observations. The analysis on tides indicates that the diurnal tide is dominant at Wuhan. The seasonal variability is observed in both the diurnal and semidiurnal tidal amplitudes with the maximum values occurring usually near the equinoxes. Compared with the Global Scale Wave Model (GSWM00), the observed results generally show a smaller diurnal tidal amplitude and a larger semidiurnal tidal amplitude. Key words: Meteor radar, mean winds, tides, MLT dynamics. The terdiurnal tide in the mesosphere and lower thermosphere over Wuhan (30 %N , 1 1 4 %E ) G u a n g x i n Z h a o 1 , 2 , 3 , L i b o L i u 1 , B a i q i N i n g 1 , W e i x i n g W a n 1 , a n d J i a n g a n g X i o n g 1 1 I n s t i t u t e o f G e o l o g y a n d G e o p h y s i c s , C h i n e s e A c a d e m y o f S c i e n c e s , B e i j i n g , 1 0 0 0 2 9 , C h i n a 2 W u h a n I n s t i t u t e o f P h y s i c s a n d M a t h e m a t i c s , C h i n e s e A c a d e m y o f S c i e n c e s , Wuhan, China 3 Graduate School of the Chinese Academy of Sciences, China (Received August 25, 2004; Revised April 18, 2005; Accepted April 18, 2005) Winds measured by an all-sky meteor radar have been used to investigate the terdiurnal tide in the mesosphere and lower thermosphere (MLT) region overWuhan (30.6 %N , 1 1 4 . 4 %E ) . W e p r e s e n t a c l i m a t o l o g y o f t h e t e r d i u r n a l t i d e a t l o w - m i d l a t i t u d e s i t e d u r i n g t h e p e r i o d o f A p r i l 2 0 0 2 t o D e c e m b e r 2 0 0 4 . T h e t e r d i u r n a l p e a k i s d i s t i n c t i n t h e l o n g - t e r m p o w e r s p e c t r u m o f t h e w i n d . T h e m o n t h l y a n d s e a s o n a l m e a n m a x i m u m a m p l itudes have values of 7 m/s and 5 m/s, respectively. The short-term amplitudes can occasionally reach up to 30 m/s, and at times the terdiurnal tide is as large as the diurnal and semidiurnal ones. It seems that the meridional component is more regular than the zonal one. An obvious annual variation is observed in the meridional phases with a phase leading in winter than that in summer. The annual variation for the terdiurnal tidal amplitude is not obvious, and is variable from year to year in our observatio n s . T h i s s e a s o n a l t r e n d i s s l i g h t l y d i f f e r e n t f r o m e a r l i e r s t u d i e s a t o t h e r l o c a t i o n s . K e y w o r d s : M e t e o r r a d a r , t e r d i u r n a l t i d e , m e s o s p h e r i c d y n a m i c s , n o n l i n e a r i n t e r a c t i o n . R e s p o n s e s o f e q u a t o r i a l a n o m a l y t o t h e c t o b e r "N o v e m b e r 2 0 0 3 s u p e r s t o r m s B . Z h a o1,2,3,W.Wan1, and L. Liu1 1 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2 Wuhan Institute of Physics and Mathematics, CAS, Wuhan 430071, China 3 Graduate School of Chinese Academy of Sciences, Beijing, China Received: 8 May 2004 Revised: 2 December 2004 Accepted: 16 December 2004 Published: 30 March 2005 Abstract. The responses of Equatorial Ionization Anomaly (EIA) to the superstorms of October "N o v e m b e r 2 0 0 3 w e r e i n v e s t i g a t e d u s i n g t h e t o t a l e l e c t r o n c o n t e n t ( T E C ) m e a s u r e d w i t h g l o b a l p o s i t i o n i n g s y s t e m ( G P S ) r e c e i v e r s i n C h i n a , S o u t h e a s t A s i a , A u s t r a l i a n ( C S A A ) , a n d t h e A m e r i c a n r e g i o n s . E n h a n c e d E I A w a s s e e n t o b e c o r r e l a t e d w i t h t h e s o u t h w a r d turning of the interplanetary magnetic field Bz. In both the CSAA and American regions, EIA was intensified, corresponding to a large increase in the F-layer peak height (hmF2) measured by ionosonde and digisonde at middle and equatorial latitudes. However, the enhanced EIA was shown to be more significant during the daytime in the American region, which was associated with a series of large substorms when Bz was stable southward. The prompt penetration electric field and the wind disturbances dynamo electric field are suggested to be responsible for this observation according to current theory, although some features cannot be totally decipherable. Both the ionogram and magnetometer data show the existence of a weak shielding effect whose effect still needs further study. A clear asymmetric ionospheric response was shown in our TEC observations, even though it was only one month after autumnal equinox. The southern EIA crest was totally obliterated on 29 and 30 October in the CSAA region and on 31 October in the American region. Ion temperatures from the Defense Meteorological Satellite Program (DMSP) spacecraft revealed that the unequal energy injection at the polar region might be the reason for this effect. It is concluded that different physical processes have varying degrees of importance on the evolution of EIA in the CSAA and American regions. Keywords. Ionosphere (Equatorial ionosphere; Ionospheremagnetosphere interactions; Ionospheric disturbances) Lunar tidal winds in the mesosphere over Wuhan and Adelaide Xiaojuan Niua,b,c, Jiangang Xionga, Weixing Wana, Baiqi Ninga, Libo Liua, R.A. Vincentd, I.M. Reidd a Institute of Geology and Geophysics, Chinese Academy of Science, P.O. Box 9825, Beijing 100029, P.R. China b Wuhan Institute of Physics and Mathematics, Chinese Academy of Science, Wuhan430071,P.R.China c Graduate School of Chinese Academy of Sciences, Beijing, P.R. China d Department of Physics and Mathematical physics, University of Adelaide, Adelaide, SouthAustralia, Australia Received 14 October 2004; received in revised form 18 August 2005; accepted 18 August 2005 Abstract Based on measurements made from 2002 to 2003 in the 8098 km region by the Wuhan meteor radar (31_N, 114_E) and winds observed simultaneously by the Adelaide MF radar (35_S, 138_E), the amplitude and phase of the lunar semidiurnal tide are computed and compared. There is a clear seasonal variation at both stations. A northward amplitude maximum in February is evident over Adelaide and in April over Wuhan, but the eastward amplitude maximizes in January over Wuhan and in October over Adelaide. The height variation of phase displays a 3 1 lunar hour difference, with the eastward component leading the northward component for most months at Adelaide and eastward wind lagging the northward wind at Wuhan. Comparisons of phases between Wuhan and Adelaide suggest that an anti-symmetric tide may be dominant in March, April, June and July and a symmetric tide in January, September and December. _ 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Lunar tides; Lunar semidiurnal tide; Mesosphere The 16-day waves in the mesosphere and lower thermosphere over Wuhan (30.6_N, 114.5_E) and Adelaide (35_S, 138_E) Guo-ying Jianga,b,c, Jian-Gang Xiong , Wei-Xing Wana, Bai-Qi Ninga, Li-Bo Liua, R.A. Vincentd, I. Reid a Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, PR China b Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, P.O. Box 71010, Wuhan 430071, PR China c Graduate School of Chinese Academy of Sciences, Beijing, PR China d Department of Physics and Mathematical Physics, University of Adelaide, Adelaide, SA, Australia Received 14 October 2004; received in revised form 2 March 2005; accepted 2 March 2005 Abstract Winds from a meteor radar at Wuhan (30.6_N, 114.5_E) and a MF radar at Adelaide (35_S, 138_E) are used to study the 16-day waves in the mesosphere and lower thermosphere (MLT). The height range is 7898 km at Wuhan and 7098 km at Adelaide. By comparison, it is found that the zonal components at both sites are generally larger than the meridional ones, and eastward motion of the zonal background winds is favorable for the 16-day waves penetration to the MLT region. The zonal maximum amplitude appears in the autumn (SeptemberOctober) around 8698 km at Wuhan and in the winter months and early spring (JulyOctober) around 7282 km at Adelaide. Differences are found in wave amplitudes and time of appearance between the two years of 2002 and 2003. In 2003, the intensity of the wave amplitudes is relatively smaller than that for 2002 at both sites. The summer 16-day waves are comparatively weaker at Adelaide in both years, but stronger in 2002 at Wuhan near the mesopause and the lower thermosphere (8698 km). The strong summer waves at Wuhan may come from the winter southern hemisphere. _ 2005 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: 16-day waves; Mesosphere and lower thermosphere; Planetary wave Statistical characteristics of the total ion density in the topside ionosphere during period 1996-2004 by using Empirical orthogonal function (EOF) analysis Biqiang Zhao 1, 2, 3, Weixing Wan 1, Libo Liu 1, Xinan Yue 1, 2, 3 and Sarita Venkatraman4 1 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2 Wuhan Institute of Physics and Mathematics, CAS, Wuhan 430071, China 3 Graduate School of Chinese Academy of Sciences, Beijing, China 4 William B. Hanson Center for Space Sciences, University of Texas at Dallas, Richardson Abstract. We have applied the empirical orthogonal function (EOF) analysis to examine the climatology of the total ion density Ni at 840 km during the period 1996-2004 obtained from the Defense Meteorological Satellite Program (DMSP) spacecrafts. The data set for each of the local time (0930 LT and 2130 LT) is decomposed into a time mean plus the sum of EOF bases Ei of space multiplied by time-varying EOF coefficients Ai. Physical explanations are made on the first three EOFs which together can capture more than 95% of total variance of the original data set. Results show that the dominant mode that controls the Ni variability is the solar EUV flux, which is consistent with the results of Rich et al. (2003). The second EOF, associated with the solar declination, presents an annual (summer to winter) asymmetry that is caused by the transequatorial winds. The semiannual variation that appears in the third EOF for the evening sector is interpreted as both, the effects of the equatorial electric fields and wind patterns. Both the annual and semiannual variations are modulated by the solar flux, which has a close relationship with the O+ composition. The quick convergence of the EOF expansion makes it very convenient to construct an empirical model for the original data set. The modeled results show that the accuracy of the prediction depends mainly on the first principal component which has a close relationship with the solar EUV flux. Key words: ionosphere (Equatorial ionosphere; Modelin g a n d f o r e c a s t i n g ; S o l a r r a d i a t i o n a n d c o s m i c r a y e f f e c t t s ) fkIl NzzM L T -NQ1 6 elvAmfKm YV 1 2 3 q^R1 NkSf1 [~vP1 Rzl1 1 -NVyf[b0W(N0Wtxvz@bSN1 0 0 0 2 9 2 -NVyf[bfkIlirtNpef[xvz@b 3 -NVyf[bxvzub Xd )R(ufkIlAmf2 0 0 2 t^2 g2 0 e2 0 0 3 t^1 1 g1 0 evKmpencxvzNfkIl Nzz-NB\ NNOpB\( M L T ) -NvQ1 6 elsShTgV(W1 2 2 0 )YvLfl0 Rg~ghf 1 6 elv~TbR8^k~TbR:_ ( 1 ) (W2 0 0 2 t^T2 0 0 3 t^l/cE^ g:_Qs(WS_t^vyc[( ~9 g1 0 e N1 0 g1 0 e) L o m b S c a r g l e ( L S ) 1Rg_0R/cE^ g'Y