An index to describe global ionospheric variability using satellite-borne solar EUV ... ·...
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An index to describe global ionospheric variability using satellite-borne solar EUV measurements C. Unglaub 1 , Ch. Jacobi 1 , G. Schmidtke 2 , B. Nikutowski 1,2 , R. Brunner 2 1 University of Leipzig, Institute for Meteorology, Stephanstr. 3, 04103 Leipzig, Germany 2 Fraunhofer IPM, Heidenhofstraße 8, 79110 Freiburg, Germany Summary Primary ionisation of major ionospheric constituents is calculated from SolACES and TIMED-SEE solar EUV measurements in the wavelength range 16-135 nm, and number densities of the background atmosphere taken from the NRLMSIS-E climatology. From the calculated ionisation rates, a global EUV-TEC index is derived, which describes the ionospheric response on solar EUV and its variability from the last solar maximum to date. The index is compared against global mean ionisation values taken from TEC maps. The index describes global TEC variability better than other indices like F10.7 do. The EUV-TEC index may be used for scientific research, and to describe the ionospheric effects on radio communication and navigation systems. Data and calculation of the EUV-TEC Index Results Daily TIMED/SEE solar EUV fluxes, and Fig. 5: Time series of daily EUV-TEC indices and global mean TEC (upper panel) and time series for global mean TEC index and F10.7 solar radio flux (lower panel) during 2002 to 2009. Few SolACES data are shown as blue stars. Fig. 6: EUV-TEC index (left panel) and F10.7 (right panel) vs. global mean TEC during 2002 to 2009. Few SolACES data are shown by blue stars. Different time scales Daily TIMED/SEE solar EUV fluxes, and some additional spectra from SolACES. Wavelength range from 16-135nm is used. Fig. 1: Example of SolACES and TIMED/SEE spectra. Global mean background atmosphere from NRLMSISE-00 Fig. 2: Daily mean NRLMSISE-00 number densities at 0°E, 0°N of four atmospheric gases for different solar activities Model to calculate primary ionisation Fig. 3: Sketch of absorption/ionisation calcula- tion for a specific point with given zenith angle. Fig. 4: Example (15.04.2005 ) of primary photo- ionisation profiles for different zenith distances. Global mean ionisation provides EUV-TEC index. Comparison with F10.7 and global Conclusions From solar EUV spectra, global mean primary ionisation rates have been calculated on a daily basis. This provides an index - EUV-TEC -, which to a certain degree describes the influence of solar variability on the ionosphere. Comparison of the index variability with that of global mean TEC provided by GPS measurements show that the index is strongly correlated with TEC, although it performs only slightly better than indices based on EUV flux directly. In particular, the index is able to partly represent the seasonal global TEC cycle during solar minimum, which is not present in other indices used for solar variability description. In particular, for representing ionospheric variability, the new index performs better than the frequently used F10.7 radio flux. Acknowledgements: TIMED-SEE data has been provided by LASP, University of Colorado. TEC data has been provided by NASA. F10.7 indices have been provided by NGDC. This work was partly funded by Deutsche Forschungsgemeinschaft under grant JA 836/24-1 . Contact, information and data: Christoph Jacobi Institut für Meteorologie, Universität Leipzig, Stephanstr. 3, 04103 Leipzig Email: [email protected] printed at Rechenzentrum Leipzig poster available on http://www.uni-leipzig.de/~jacobi/collm/poster.htm Fig. 7: 301 pt running correlation of global mean TEC vs. EUV energy flux, F10.7, and EUV-TEC. Left panel: original daily data. Middle panel: 60 days high-pass filtered data. Right panel: 60 days low-pass filtered data (Lanczos filter, 100 weights). The weaker correlation during winter seasons is due to the semiannual TEC variation not driven by EUV. Fig. 8: Global mean TEC and EUV-TEC index for high/moderate (left panel) and low (right panel) solar activity. The thick solid line represents 60 days low-pass filtered data (Lanczos filter, 100 weights). During solar minimum TEC is dominated by the seasonal cycle, including the semiannual oscillation not driven by EUV variations. index. Comparison with F10.7 and global mean IGS TEC.
Transcript of An index to describe global ionospheric variability using satellite-borne solar EUV ... ·...
An index to describe global ionospheric variability using satellite-borne solar EUV measurements
C. Unglaub1, Ch. Jacobi1, G. Schmidtke2, B. Nikutowski1,2, R. Brunner2
1University of Leipzig, Institute for Meteorology, Stephanstr. 3, 04103 Leipzig, Germany2Fraunhofer IPM, Heidenhofstraße 8, 79110 Freiburg, Germany
Summary
Primary ionisation of major ionospheric constituents is calculated fromSolACES and TIMED-SEE solar EUV measurements in the wavelengthrange 16-135 nm, and number densities of the background atmospheretaken from the NRLMSIS-E climatology. From the calculated ionisationrates, a global EUV-TEC index is derived, which describes the ionosphericresponse on solar EUV and its variability from the last solar maximum todate. The index is compared against global mean ionisation values takenfrom TEC maps. The index describes global TEC variability better thanother indices like F10.7 do. The EUV-TEC index may be used for scientificresearch, and to describe the ionospheric effects on radio communicationand navigation systems.
Data and calculation of the EUV-TEC Index
Results
Daily TIMED/SEE solar EUV fluxes, and
Fig. 5: Time series of daily EUV-TEC indices and global mean TEC (upper panel) andtime series for global mean TEC index and F10.7 solar radio flux (lower panel) during2002 to 2009. Few SolACES data are shown as blue stars.
Fig. 6: EUV-TEC index (left panel) and F10.7 (right panel) vs. global mean TECduring 2002 to 2009. Few SolACES data are shown by blue stars.
Different time scales
Daily TIMED/SEE solar EUV fluxes, andsome additional spectra from SolACES.Wavelength range from 16-135nm is used.
Fig. 1: Example of SolACES and TIMED/SEE spectra.
Global mean background atmospherefrom NRLMSISE-00
Fig. 2: Daily mean NRLMSISE-00 numberdensities at 0°E, 0°N of four atmospheric gasesfor different solar activities
Model to calculate primary ionisation
Fig. 3: Sketch of absorption/ionisation calcula-tion for a specific point with given zenith angle.
Fig. 4: Example (15.04.2005 ) of primary photo-ionisation profiles for different zenith distances.
Global mean ionisation provides EUV-TECindex. Comparison with F10.7 and global
Conclusions
From solar EUV spectra, global mean primary ionisation rates have beencalculated on a daily basis. This provides an index - EUV-TEC -, which to acertain degree describes the influence of solar variability on theionosphere. Comparison of the index variability with that of global meanTEC provided by GPS measurements show that the index is stronglycorrelated with TEC, although it performs only slightly better than indicesbased on EUV flux directly. In particular, the index is able to partlyrepresent the seasonal global TEC cycle during solar minimum, which isnot present in other indices used for solar variability description. Inparticular, for representing ionospheric variability, the new index performsbetter than the frequently used F10.7 radio flux.
Acknowledgements:
TIMED-SEE data has been provided by LASP, University of Colorado. TECdata has been provided by NASA. F10.7 indices have been provided byNGDC. This work was partly funded by Deutsche Forschungsgemeinschaftunder grant JA 836/24-1 .
Contact, information and data:
Christoph JacobiInstitut für Meteorologie, Universität Leipzig, Stephanstr. 3, 04103 LeipzigEmail: [email protected]
printed at Rechenzentrum Leipzig poster available on http://www.uni-leipzig.de/~jacobi/collm/poster.htm
Fig. 7: 301 pt running correlation of global mean TEC vs. EUV energy flux, F10.7,and EUV-TEC. Left panel: original daily data. Middle panel: 60 days high-pass filtereddata. Right panel: 60 days low-pass filtered data (Lanczos filter, 100 weights). Theweaker correlation during winter seasons is due to the semiannual TEC variation notdriven by EUV.
Fig. 8: Global mean TEC and EUV-TEC index for high/moderate (left panel) and low(right panel) solar activity. The thick solid line represents 60 days low-pass filtereddata (Lanczos filter, 100 weights). During solar minimum TEC is dominated by theseasonal cycle, including the semiannual oscillation not driven by EUV variations.
index. Comparison with F10.7 and globalmean IGS TEC.
