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URSIGA, New Delhi, 23-29 Oct 2005 Coordinated Observations of Ionospheric Scintillations, Density Profiles and Total Electron Content on a Common Magnetic.

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Presentation on theme: "URSIGA, New Delhi, 23-29 Oct 2005 Coordinated Observations of Ionospheric Scintillations, Density Profiles and Total Electron Content on a Common Magnetic."— Presentation transcript:

1 URSIGA, New Delhi, Oct 2005 Coordinated Observations of Ionospheric Scintillations, Density Profiles and Total Electron Content on a Common Magnetic Flux Tube K. M. Groves 1, S. Basu 1, T. R. Pedersen 1 T. L. Beach 1, J. M. Quinn 1, B. Taliaferro 1 E. R. de Paula, I. S. Batista, M. A. Abdu, R.C. Livingston, P. Ning, C. Carrano 1 Space Vehicles Directorate Space Weather Center of Excellence Air Force Research Laboratory 2005 URSI General Assembly, New Delhi, India GF1B: Atmosphere-Ionosphere Sounding by Using Global Navigation Satellite Systems

2 URSIGA, New Delhi, Oct 2005 Spread F Meridional Dependence Motivation: Regional specification from 1-D measurements COPEX Campaign Overview Ionospheric variations at conjugate locations Summary Outline

3 URSIGA, New Delhi, Oct 2005 Data Assimilation Methods Constraining model output Developing statistical interpolation techniques Adjusting model drivers –Kalman filter –Adjoint methods Real-time Scintillation Nowcasting from Space The satellite provides only a one-dimensional sampling of the parameters. Need to specify the ionosphere in 3-D Communication/Navigation Outage Forecast System (C/NOFS)

4 URSIGA, New Delhi, Oct 2005 Motivation: Observation Extrapolation The Challenge: Map 1-D scintillation estimates into 2-D representations Satellite measurement ground track Current assumption: Symmetry about the magnetic equator— Inconsistent with asymmetric density structure near solstice Simulated scintillation structures

5 URSIGA, New Delhi, Oct 2005 COPEX Campaign Oct-Nov 2002 Magnetic equator & conjugate location observations Conducted by INPE with AFRL & University collaboration Objective is to understand initiation, growth and dynamics of young plume structures Critical to understanding large- scale structure of depletion development Multi-diagnostics at three locations will measure required ionospheric parameters

6 URSIGA, New Delhi, Oct 2005 Principal Instrumentation Instruments operated from Oct to 07 Dec 2002 Sites on common flux tube; Campo Grande and Boa Vista magnetically conjugate Combination of these data with available ROCSAT passes and other ancillary data sets provide basis to investigate meridional variations in detail Campo GrandeCachimbo/ *Alta FlorestaBoa Vista Digisonde VHF scint & drift GPS TEC & scint All-sky imager Digisonde VHF scint & drift GPS TEC & scint All-sky imager Digisonde VHF scint & drift* GPS TEC & scint* All-sky imager VHF coherent backscatter radar* GEO 20.5S 54.7W 9.5S 54.8W/ 9.9S 56.1W 2.8N 60.7W MAG 10.8S 14.0E 0.7S 15.2E 12.6N 13.5E

7 URSIGA, New Delhi, Oct 2005 Mlat VTEC TEC Structure Oct-Nov 2002 TEC data reveals asymmetric anomaly structure driven by inter- hemispheric neutral wind Mean TEC levels decreasing ~30%+ from October to December Local Time VTEC Mlat Local Time VTEC October 3-9 November 1-7 December

8 URSIGA, New Delhi, Oct 2005 Mlat S4 S4 Structure Oct-Nov 2002 GPS L1 (1575 MHz) Scintillation Scintillation activity and intensity peak in December despite ~20% decrease in overall peak density Scintillation intensity symmetric as a function of magnetic latitude Local Time S4 Mlat Local Time S October 3-9 November 1-7 December

9 URSIGA, New Delhi, Oct 2005 Examine daily plots between UT (~ LT) No observations below 30° elevation angle used in analysis Consider results statistically when scintillation occurred and data was present at both “high latitude” stations CGR AFL BVB Analysis Approach

10 URSIGA, New Delhi, Oct 2005 TEC Characterization Overall TEC decreases 20-50% from October to December Largest decreases observed in southern anomaly North/South TEC ratio increases from 1.2 in October to about 1.4 in December (40% higher!) Avg TEC UT North/South Ratio

11 URSIGA, New Delhi, Oct 2005 Peak Density Characterization On average, F0F2 remains relatively constant over observing period Largest decreases observed in southern anomaly North/South F0F2 ratio increases from unity in October to about 1.1 in December (approximately 20% higher peak density) Variations increase significantly during latter half of campaign –May be related to reading ionograms with increased spread F Avg F0F UT North/South F0F2 Ratio

12 URSIGA, New Delhi, Oct 2005 Slab Thickness Effective slab thickness (TEC/NmF2) exhibits similar decrease over time Thicknesses generally 10-20% greater in northern hemisphere, becoming quite variable during 2 nd half of campaign (Nov-Dec) Avg Slab Thickness UT North/South Slab Thickness Ratio

13 URSIGA, New Delhi, Oct 2005 What About Scintillation? ~10% decrease in S4 (   N) over campaign period not entirely consistent with decrease in NmF2 (~20%) North/south ratio is essentially unity (no asymmetry)

14 URSIGA, New Delhi, Oct 2005 Statistical View Distribution of scintillation activity and intensity are statistically identical in both hemispheres despite differences in TEC and, to lesser extent, F0F2 Activity increases in frequency during latter half of campaign Intensity distribution is essentially unchanged (2-3% decrease in monthly statistics) 795 Samples Percentile S4 25: : : : Samples Percentile S4 25: : : : Samples Percentile S4 25: : : : Samples Percentile S4 25: : : : a)b) c) d)

15 URSIGA, New Delhi, Oct 2005 Scintillation intensity appears relatively independent of background TEC variations near the anomaly crests TEC decreases markedly approaching summer solstice, particularly in the southern magnetic hemisphere; change in NmF2 less than half observed TEC decrease On average TEC, NmF2 and slab thickness greater in the northern magnetic hemisphere during this time period (Oct- Dec 2002) S4 appears to be essentially symmetric at the same magnetic latitude in both hemispheres, despite variations in TEC, slab thickness, and NmF2 Vertical distribution of irregularities non-homogenous; propagation effects dominated by layer near F-region peak Conclusions


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