Ancillary Data Sources

1
2005 URSI General Assembly, New Delhi,
India GF1B Atmosphere-Ionosphere Sounding by
Using Global Navigation Satellite Systems
Coordinated Observations of Ionospheric
Scintillations, Density Profiles and Total
Electron Content on a Common Magnetic Flux Tube
K. M. Groves1, S. Basu1, T. R. Pedersen1 T.
L. Beach1, J. M. Quinn1, B. Taliaferro1E. R. de
Paula, I. S. Batista, M. A. Abdu, R.C.
Livingston, P. Ning, C. Carrano 1Space Vehicles
Directorate Space Weather Center of
Excellence Air Force Research Laboratory
2
Spread F Meridional Dependence
Outline

• Motivation Regional specification from 1-D
  measurements
• COPEX Campaign Overview
• Ionospheric variations at conjugate locations
• Summary

3
Real-time Scintillation Nowcastingfrom Space
Communication/Navigation Outage Forecast System
(C/NOFS)
The satellite provides only a one-dimensional
sampling of the parameters. Need to specify the
ionosphere in 3-D

• Data Assimilation Methods
• Constraining model output
• Developing statistical interpolation techniques
• Adjusting model drivers
• Kalman filter
• Adjoint methods

4
Motivation Observation Extrapolation
The Challenge Map 1-D scintillation estimates
into 2-D representations
Simulated scintillation structures
Satellite measurement ground track
Current assumption Symmetry about the magnetic
equatorInconsistent with asymmetric density
structure near solstice
5
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
Principal Instrumentation
Campo Grande Cachimbo/ Alta Floresta Boa Vista
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

• 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

7
TEC Structure Oct-Nov 2002
13-19 October

• TEC data reveals asymmetric anomaly structure
  driven by inter-hemispheric neutral wind
• Mean TEC levels decreasing 30 from October to
  December

1-7 December
3-9 November
8
S4 Structure Oct-Nov 2002GPS 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

S4
13-19 October
Mlat
S4
S4
3-9 November
1-7 December
Mlat
Local Time
Local Time
9
Analysis Approach

• Examine daily plots between 0000-0200 UT
  (2030-2230 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

10
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 00-02 UT
North/South Ratio
11
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

North/South F0F2 Ratio
Avg F0F2 00-02 UT
12
Slab Thickness

• Effective slab thickness (TEC/NmF2) exhibits
  similar decrease over time
• Thicknesses generally 10-20 greater in northern
  hemisphere, becoming quite variable during 2nd
  half of campaign (Nov-Dec)

North/South Slab Thickness Ratio
Avg Slab Thickness 00-02 UT
13
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
Statistical View

• Distribution of scintillation activity and
  intensity are statistically identical in both
  hemispheres despite differences in TEC and, to
  lesser extent, F0F2

877 Samples Percentile S4 25
0.329 50 0.363 75 0.417 90 0.482
795 Samples Percentile S4 25
0.333 50 0.371 75 0.426 90 0.479
a)
b)

• Activity increases in frequency during latter
  half of campaign
• Intensity distribution is essentially unchanged
  (2-3 decrease in monthly statistics)

c)
d)
1083 Samples Percentile S4 25
0.324 50 0.357 75 0.408 90 0.457
895 Samples Percentile S4 25
0.328 50 0.366 75 0.416 90 0.467
15
Conclusions

• 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