The Timevarying Ionosphere. measured by GPS The Timevarying Ionosphere measured by GPS Presented by: Jakob Jakobsen
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 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 2
Timeserie Dual frequency data with 30 second sampling rate Three stations 130 - 207 km. separation 56°N latitude Timeseries (1999-2007) calculated using a Kalman Filter estimating Absolute TEC Latitude variation Longitude variation NNF: High Precision Navigation and Positioning | 10. June 2008 | page 3
Observation model SV1 SV2 SV3 Icenter IP12 SV4 IP22 IP11 IP21 Rx2 Rx1 400 km NNF: High Precision Navigation and Positioning | 10. June 2008 | page 4
Kalman filter 1: 2: 3: 4: 5: Given and : NNF: High Precision Navigation and Positioning | 10. June 2008 | page 5
General Ionospheric Timevarying Parameters Daily Yearly 11 year period Follow the length of day Highest during equinoxes NNF: High Precision Navigation and Positioning | 10. June 2008 | page 6
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. NNF: High Precision Navigation and Positioning | 10. June 2008 | page 7
First eigenvalue 2004 U1 S V1 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 8
NNF: High Precision Navigation and Positioning | 10. June 2008 | page 9
Second eigenvalue 2004 U2 S V2 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 10
NNF: High Precision Navigation and Positioning | 10 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 11
Third eigenvalue 2004 U3 S V3 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 12
NNF: High Precision Navigation and Positioning | 10 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 13
Correlation with Sunspot Number Coefficients 0.93 – 0.97 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 14
Generated Ionospheric model of absolute TEC, 2004 NNF: High Precision Navigation and Positioning | 10. June 2008 | page 15
Models generated NNF: High Precision Navigation and Positioning | 10. June 2008 | page 16
Power spectrum NNF: High Precision Navigation and Positioning | 10. June 2008 | page 17
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. NNF: High Precision Navigation and Positioning | 10. June 2008 | page 18
Jakob Jakobsen jj@space.dtu.dk http://www.heisesgade.dk NNF: High Precision Navigation and Positioning | 10. June 2008 | page 19