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The number of satellite overflights over the
whole observation period with respect to minimum threshold elevation. |
In the paper, we show that ionospheric tomography results are modulated by the solar cycle, which can be seen from the analysed data. We have altogether measured over 66,000 flybys of the Russian COSMOS beacon satellites. For the analysis, we used only north-to-south flights, because they are along the SGO ionospheric tomography chain.
In the figure below, we have plotted the analysed total electron content (VTEC) values over Kokkola, Finland (averaged from 11-14 MLT). These are compared to the well-established Sun activity indices, the sunspot number and the solar flux index F10.7.
Norberg, J., Roininen, L., Kero, A., Raita, T., Ulich, T., Markkanen, M., Juusola, L., and Kauristie, K.: Sodankylä ionospheric tomography dataset 2003–2014, Geosci. Instrum. Method. Data Syst. Discuss., 5, 385-404, doi:10.5194/gid-5-385-2015, 2015.
... and here's the abstract:
Sodankylä Geophysical Observatory has been operating a tomographic receiver network and collecting the produced data since 2003. The collected dataset consists of phase difference curves measured from Russian COSMOS dual-frequency (150/400 MHz) low-Earth-orbit satellite signals, and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of the tomographic system. During the observation period, 2003–2014, there were three-to-five operational stations at the Fenno-Scandinavian sector. Altogether the analysis consists of around 66 000 overflights, but to ensure the quality of the reconstructions, the examination is limited to cases with descending (north to south) overflights and maximum elevation over 60°. These constraints limit the number of overflights to around 10 000. Based on this dataset, one solar cycle of ionospheric vertical total electron content estimates is constructed. The measurements are compared against International Reference Ionosphere IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.
... and here's the abstract:
Sodankylä Geophysical Observatory has been operating a tomographic receiver network and collecting the produced data since 2003. The collected dataset consists of phase difference curves measured from Russian COSMOS dual-frequency (150/400 MHz) low-Earth-orbit satellite signals, and tomographic electron density reconstructions obtained from these measurements. In this study vertical total electron content (VTEC) values are integrated from the reconstructed electron densities to make a qualitative and quantitative analysis to validate the long-term performance of the tomographic system. During the observation period, 2003–2014, there were three-to-five operational stations at the Fenno-Scandinavian sector. Altogether the analysis consists of around 66 000 overflights, but to ensure the quality of the reconstructions, the examination is limited to cases with descending (north to south) overflights and maximum elevation over 60°. These constraints limit the number of overflights to around 10 000. Based on this dataset, one solar cycle of ionospheric vertical total electron content estimates is constructed. The measurements are compared against International Reference Ionosphere IRI-2012 model, F10.7 solar flux index and sunspot number data. Qualitatively the tomographic VTEC estimate corresponds to reference data very well, but the IRI-2012 model are on average 40 % higher of that of the tomographic results.
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VTEC values over Kokkola averaged from 11-14 MLT
versus corresponding IRI-2012 model values, sunspot number and solar flux index F10.7. |
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