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| Titel |
Extreme ultraviolet spectral irradiance measurements since 1946 |
| VerfasserIn |
G. Schmidtke |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-5010
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| Digitales Dokument |
URL |
| Erschienen |
In: History of Geo- and Space Sciences ; 6, no. 1 ; Nr. 6, no. 1 (2015-03-18), S.3-22 |
| Datensatznummer |
250115432
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| Publikation (Nr.) |
 copernicus.org/hgss-6-3-2015.pdf |
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| Zusammenfassung |
| In the physics of the upper atmosphere the solar extreme
ultraviolet (EUV) radiation plays a dominant role controlling most of the
thermospheric/ionospheric (T/I) processes. Since this part of the solar
spectrum is absorbed in the thermosphere, platforms to measure the EUV
fluxes became only available with the development of rockets reaching
altitude levels exceeding 80 km. With the availability of V2 rockets used in
space research, recording of EUV spectra started in 1946 using photographic
films. The development of pointing devices to accurately orient the
spectrographs toward the sun initiated intense activities in
solar–terrestrial research. The application of photoelectric recording
technology enabled the scientists placing EUV spectrometers aboard
satellites observing qualitatively strong variability of the solar EUV
irradiance on short-, medium-, and long-term scales. However, as more
measurements were performed more radiometric EUV data diverged due to the
inherent degradation of the EUV instruments with time. Also, continuous
recording of the EUV energy input to the T/I system was not achieved. It is only
at the end of the last century that there was progress made in solving the serious
problem of degradation enabling to monitore solar EUV fluxes with sufficient
radiometric accuracy. The data sets available allow composing the data
available to the first set of EUV data covering a period of 11 years for
the first time. Based on the sophisticated instrumentation verified in space,
future EUV measurements of the solar spectral irradiance (SSI) are promising
accuracy levels of about 5% and less. With added low-cost equipment,
real-time measurements will allow providing data needed in ionospheric
modeling, e.g., for correcting propagation delays of navigation signals from
space to earth. Adding EUV airglow and auroral emission monitoring by
airglow cameras, the impact of space weather on the terrestrial T/I system
can be studied with a spectral terrestrial irradiance camera (STI-Cam) and
also be used investigating real-time space weather effects and deriving more
detailed correction procedures for the evaluation of Global Navigation
Satellite System (GNSS) signals. Progress in physics goes with achieving
higher accuracy in measurements. This review historically guides the
reader on the ways of exploring the impact of the variable solar radiation in
the extreme ultraviolet spectral region on our upper atmosphere in the
altitude regime from 80 to 1000 km. |
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