On Local-Time Dependent Deviations in the Ionospheric Density Profiles Retrieved From the Radio Occultation Dada

Transcription

1 On Local-Time Dependent Deviations in the Ionospheic Density Pofiles Retieved Fom the Radio Occultation Dada S.-Y. Su 1, S. Tulasi Ram,3, and C. H. Liu 1. National Cental Univesity, Chung-Li, Taiwan.. Academia Sinica, Taipei, Taiwan. 3. RISH, Kyoto Univesity, Kyoto, Japan.

2 FORMOSAT-3/COSMIC Radio Occultation (RO Measuements GPS-F3/COSMIC RO data is inveted with assumption that the ionospheic density distibution is spheically symmetic. Deviations in the ionospheic pofiles ae noticed. Such deviations will also show local-time (LT dependence.

3 Compute Simulated Retieval Deviations Retieval deviation of the thee-peak-and-two-valley in the latitudinal density distibution (Yue et al., 009.

4 Reconstucted (Tue Ionospheic Pofiles Reconstuct an ionospheic pofile by connecting the C/NOFS IVM data at ~700 km altitude to the ionosonde measued F peak data with the α - Chapman function (Tulasi Ram et al., 009. Veify the econstucted pofile with the Jicamaca incoheent scatte ada (ISR. Constuct many pofiles to obtain a mean pofile fo compaison.

5 Data Used in this Study Digisonde data fom Jicamaca C/NOFS in-situ ion density F3/C ion density pofiles Peiod of Data Sep Oct 008 & Ma-Ap 009 (Equinox

6 Examples showing the econstuction of topside Ne(h pofile using C/NOFS- IVM in-situ density Mach 4, 009 Mach 5, 009 C/NOFS 11 LT 1 LT C/NOFS α- Chapman function 1 z N( h = NmF.exp[.(1 z e ] ( h hm F z = HT

7 JICAMARCA Equinoxes 1400 LT Compaison of mean pofiles

8 Summay of compaison - Equinoxes 0600 LT 100 LT 1800 LT Undeestimates Oveestimates Oveestimates 0800 LT 1400 LT 000 LT Undeestimates Oveestimates Undeestimates 1000 LT 1600 LT 00 LT Oveestimates Oveestimates Undeestimates

9 Remaks of the RO Retieved Deviations Deviations ae local-time (LT dependent. In the equatoial egion, the F3/COSMIC RO etieved data oveestimate in 10 to 18 LT secto. The RO etieved data will undeestimate in 6 to 8, and 0 to LT sectos. The eason is the fomation of the equatoial ionization anomaly (EIA at diffeent LT hous.

10 Coplana RO Geomety fo Simple Illustation

11 The diffeence between two consecutive obsevations. ( TEC ji = ( TEC ( ( TEC 0 j ( 0 i = j ( 0 j i 0 0 N( dx ( i N( j dx i 0, i =0, 1,,, and j =i+1

12 Then we have 1 ]( ( ( [( ( j i i j ji N N TEC + = ] ( ]{[( ( ( [ j k j k k k k i k N N + + = = ( ( ( ( TEC N N = = and The whole pofile can then be obtained using the ecusive fomula with efeence to the figue. k =i 1, 1,,3... ]}, ( [( = = i j i i k i k

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14 Excess (Deficiency in the Retieved Density Assume the non-unifom density distibution T m H m i e L xp N N + = (1 Then the excess (deficient TEC is L e N p TEC i H m excess T m i ( (

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16 Cause of Deviation The assumption of spheical symmetic distibution will take some aveaged value within aea of nonunifom density distibution. The etieved esult will ove-estimate the tue value The etieved esult will ove-estimate the tue value in the egion whee the suounding value is lage than the etieval egion, and unde-estimate if it is located at high density egion than the suounding.

17 Summay of compaison - Equinoxes 0600 LT 100 LT 1800 LT Undeestimates Oveestimates Oveestimates 0800 LT 1400 LT 000 LT Undeestimates Oveestimates Undeestimates 1000 LT 1600 LT 00 LT Oveestimates Oveestimates Undeestimates

18 Compute Simulated Retieval Deviations Retieval deviation of the thee-peaks-and-two-valleys in the latitudinal density distibution (Yue et al., 009.

19 Thee-Dimensional RO Data Invesion Pocedue The only assumption is still the spheical symmetic distibution in the ionospheic density. Easie to use than the Abel invesion technique because it uses only the diectly obseved (TEC.

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22 Januay 1-14, 009 Highe at mid-latitudes Lowe at low-latitudes

23 Mitigating the RO Retieval Deviation Quantify the RO etieval deviations fom a simplified lateal inhomogeneous density distibution. Use the vetical GPS TEC measuements fom gound along the GPS-F3 LOS to estimate the lateal gadient in the density inhomogeneity aound the etieval egion. Rectify the etieval deviations.

24 Thank You fo You Attention.