Coordinate Study of the Ionospheric Stratification at Low Latitude: Results from the COSMIC and GIRO Biqiang Zhao, Weixin Wan, Jie Zhu Institute of Geology and Geophysics the Chinese Academy of Sciences Beijing, P. R. China zbqjz@mail.iggcas.ac.cn Sixth FORMOSAT-3/COSMIC Data Users' Workshop
Outline Background of the ionospheric stratification Data and mhod description Features obtained from the COSMIC and GIRO Explanation for the observed features
Introduction Early observations: 9s ground ionosonde H(km) Sen, 99, JGR; Ratcliffe, 9, JGR; Bailey, 99 Equatorial ionogram Spur f fof2 D, E, F and G-layer
99 Ba Ba lan la n al. al 9. 9 99, 8, 9 Ly 2 9 n JG Hs n JG R e ia o t al. R 2 al. 2, Ba JG t is,a R t Zh a e DV ao t a l.2 al. 2 3, JA, A ST Ue NN P Za m o in to al al.2.2 Pa zn uk, G ho JA RL v Th ST am al P. pi 2 Fa al,j.2 gu AS nd TP, es Fa JG gu R a l. nd 2 es Ba, la JG a n l. R 2 a, l. Li 2 n JA 8 ST al,2 P.2 Sr 9 JG eej JG, a 2 R R Ue al JG.2 m R ot o 9,2 al.2 2, JG R 99-99, Balan renamed G-layer to F3-layer 2 What has been achieved for the ionospheric F3 layer feature? Most probably appears at Where Local time Season Solar activity Magnic activity within magnic ± morning-noon (9-2LT) Summer hemisphere Low solar activity Strong magnic storms Limitation: ionosonde station Global distribution?
2. COSMIC electron density profile (EDP) 3 millions! EDP 2 (2. -22. COSMIC: satellites, ~8 km, 2oinclination,~2 profiles of electron density and neutral temperature/day. 228
F3 layer occurrence rate Prob (DoY, LT, Mlat, Lon)=Count / Total totally ~2, EDPs within ±3 magnic latitude 2 2 =day Number of Profiles Number of Profiles 8 2 2 8 2 Day of Year 3 =.2hr 8 2 3 8 2 8 Local Time(hour) 2 22 2 x o 2. = Number of Profiles Number of Profiles = -3-2 - o Dip Latitude( ) 2 3 o 2.. -8-2 - Geographic Longitude(o) 2 8
Data selection criterion Step : EDP quality control a. 8< max_alt <; b. <3% (all) and.%(bottom) Remove the Physical abnormality in EDP Step 2: Track control Track_lat<3 Track_lon< Track_angle< Remove the False stratification due to Latitude horizontal gradient of Ne Lei al. 2 JGR
2. Data selection criterion Step 3: F3 layer judgment Double Peaks in the differential EDP (dne/dh) Comparison bween the EDP and ionosonde Profile Double Peaks COSMIC EDP Kwajalein ionosonde
examples o Geographic latitude() 2 3 tangent point trajectory -2 - COSMIC EDP - - - Altitude(km) 3 LT=2.9h() 8 2 3 LT=.h(2) 8 8 2 3 3... LT=9.3h() 8 F 2. 3 LT=8.8h() 8. 2 3 LT=8.3h() 8 2 2 2 2 2 F2 f (MHz) 2 8. f (MHz) LT=9.h(3) f (MHz) 3 2 f (MHz) Rrieved trace 2 2 2 F3 2 3 2 Altitude(km) 2 2.. f (MHz) 2 3 f (MHz)
Global feature of the F3 layer Occurrence Latitude dependence. Peaks at ± - 8 dip latitude (-2%) 2. Occurrence Southern hemisphere more than Northern one ±-8
Global feature of the F3 layer Occurrence Longitude dependence Seems to be correlated with wavenumber (WN) in May-August Equatorial Daytime upward drift From ROCSAT- May-Aug Nov-Feb
Global feature of the F3 layer Occurrence Local time dependence. Main Peak at -2 LT 2. Second Peak at post-suns period 2 LT (seldom reported)
2. Post-suns F3 layer (9-22LT) Mainly at equatorial area (- ~ ) Relatively higher at South America and Africa Peaks at
There are more cases in - E than - E? Real? ground?
3. GIRO observation 2 Sao Luis Jicamarca -2 - - Station Magnic Dip Lat. deg Jicamarca. Sao Luis -2. - - - Data Coverage Solar flux 2.~2.2 2.~2.2 2.-2. 8 92
M o n th Prob% (Month & Local time) 2 9 8 3 2 8 9 3 2 9 8 3 2 8 9 2 3 8 9 2 2 3 S ao L uis 2. o S F o rtale za o.higher S 8 9 2 3 8 9 2 3 P ro b occurrence rate in Jicamarca than in Sao Luis at post suns. Why? 2 P ro b (% ) M o n th 8Post-suns 9 2 2 J ic am arc a.3 o N th Daytime 2 3 P ro b (% ) M o n th 2 9 8 P ro b (% ) 8 3 2
Magnic meridian wind U from HWM 93 Explanation: When upward drift maximize, the equatorward wind develops quickly and maintains the formation of the F3 layer in Jicamarca. while the situation reverses in Sao Luis. Sao Luis vertical drift Jicamarca Sao Luis Jicamarca Meridional wind
Conclusion It is the first time the stratification structure of the F2 region is investigated by the COSMIC EDPs. The location of the F3 layer occurrence on a global scale are presented. These results indicate that the RO soundings are of sufficient high accuracy to differentiate the variation of very local and subtle structure. High occurrence of the suns F3 layer should be distinguished from the traditional morning noon F3 layer feature. The high occurrence of suns F3 layers, longitude, which appear mainly at Jicamarca, is clearly dependent on the magnic latitude as well as longitude.
Acknowledgement CDAAC team for processing the COSMIC data Dr. Xinan Yue University Corporation for Atmospheric Research, Boulder, Colorado, USA Prof. B. Reinisch for offering the DIDB database University of Massachusts Lowell