Mathematics – Logic
Scientific paper
May 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agusmsh53a..07c&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SH53A-07
Mathematics
Logic
7534 Radio Emissions, 7594 Instruments And Techniques, 7934 Impacts On Technological Systems, 7974 Solar Effects, 7999 General Or Miscellaneous
Scientific paper
GPS signals, systems, and navigation accuracy are vulnerable to a variety of space weather effects mostly caused by the ionosphere. This paper considers a different class of space weather effects on GPS signals: solar radio bursts. We present the first direct observations of GPS L1 (1.6 GHz) carrier-to-noise degradation on two different models of GPS receivers due to the solar radio burst associated with the 7 September, 2005 solar flare. The solar radio burst consisted of two periods of 1.6 GHz activity at approximately 17:40 UT and again at 18:30 UT. All the receivers that were affected by the solar radio burst were in the sun-lit hemisphere: three identical receivers were collocated at the Arecibo Observatory, and four identical receivers of a different model were located in Brazil. For both models, all GPS satellites in view were affected similarly. In some cases the decrease in the GPS L1 signal-to-noise agreed perfectly with the solar radio burst amplitudes, while in other cases there was no association. Further analysis indicated that only the right hand circularly polarized (RHCP) emissions affected the GPS signals. Since GPS signals are RHCP and GPS antennas are also RHCP, the null effect of the LHCP power confirms our hypothesis that the solar radio bursts are causal. The maximum solar radio burst power associated with the 7 September 2005 flare had a peak intensity of about 8,700 solar flux units (SFU) RHCP at 1,600 MHz, which caused a corresponding decrease in the signal- to-noise of about 2.5 dB across all visible satellites. Furthermore, an event with a peak intensity of 5,000 SFU RHCP at 1,600 MHz caused a 2 dB fade for nearly 15 minutes. To further investigate the effect of solar radio bursts, we also examined the emissions associated with the 28 October 2003 flare. Although polarization data was not available for this even, a similar association was found between 1,400 MHz solar radio power and GPS signal-to-noise degradation. The maximum degradation at GPS L1 was about 3 dB, and a degradation of 10 dB was observed on the semi-codeless L2 signal. This is larger than previously estimated by (Klobuchar et al. 1999). Although the events shown are small, scaling to historical solar radio bursts of 80,000 SFU imply a 12-15 dB drop in the signal-to-noise ratio. Furthermore, solar radio bursts affect all satellites in view of a receiver and all receivers in the sun-lit hemisphere. The implications are clear that the largest solar radio bursts could cause loss-of-tracking for inadequately designed GPS receivers. Solar radio bursts will also affect the new Galileo navigation system and all space-based augmentation systems such as WAAS and EGNOS. Kobuchar, J.A., J.M. Kunches, and A.J. VanDierendonck (1999), Eye on the Ionosphere: Potential Solar Radio Burst Effects on GPS Signal to Noise, GPS Solutions, 3(2), 69-71
Cerruti Alessandro P.
Gary Dale
Kintner Paul M.
Lanzerotti Louis
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