1. The Timevarying Ionosphere. measured by GPS
The Timevarying Ionosphere measured by GPS Presented by: Jakob Jakobsen

2. Outline Timeserie of absolute TEC from 1999-2007
General Timevarying characteristics
SVD analysis
Representation of the eigenvalues and relation to timevarying parameters
2004 as an example
Generated models
Power spectrum
Conclusion
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3. Timeserie Dual frequency data with 30 second sampling rate
Three stations
km. separation
56°N latitude
Timeseries ( ) calculated using a Kalman Filter estimating
Absolute TEC
Latitude variation
Longitude variation
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4. Observation model SV1 SV2 SV3 Icenter IP12 SV4 IP22 IP11 IP21 Rx2 Rx1
400 km
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5. Kalman filter 1: 2: 3: 4: 5: Given and :
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6. General Ionospheric Timevarying Parameters
Daily
Yearly
11 year period
Follow the length of day
Highest during equinoxes
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7. Singular Value Decomposition (SVD)
For each year one matrix 96 = * *
365 U1 U2 U3 S1 S2 S3 V1 V2 V3
X = U S VT
U and V are orthogonal matrices, and S is a diagonal matrix consisting
of singular values.
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8. First eigenvalue 2004
U S V1
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9. NNF: High Precision Navigation and Positioning | 10. June 2008 | page 9

10. Second eigenvalue 2004
U S V2
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11. NNF: High Precision Navigation and Positioning | 10
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12. Third eigenvalue 2004
U S V3
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14. Correlation with Sunspot Number
Coefficients
0.93 – 0.97
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15. Generated Ionospheric model of absolute TEC, 2004
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16. Models generated
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17. Power spectrum
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18. Conclusions
The first three eigenvalues represent the main characteristics of the time varying ionosphere for a year
The eigenvalues for each year show a clear correlation with the sunspot number with a correlation coefficients from 0.93 – 0.97
The power spectrum for time series show a clear daily and yearly signal, with amplitude of 7.4 and 2.8 TECU respectively.
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19. Jakob Jakobsen jj@space.dtu.dk http://www.heisesgade.dk
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