An empirical model of the extreme ultraviolet solar spectrum as a function of F-10.7

作者：Girazian Z^*; Withers P

来源：JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2015, 120(8): 6779-6794.

DOI：10.1002/2015JA021436

• solar extreme ultraviolet
• solar irradiance
• solar variability
• ionospheres
• terrestrial planets
• solar system objects

The F-10.7 solar index is frequently used as a proxy for the solar extreme ultraviolet (EUV) irradiance. However, the relationship between F-10.7 and the EUV spectrum has not been quantified in great detail for Solar Cycles 23 and 24. We use more than 2800 spectra (2003-2010) from the Solar EUV Experiment (SEE) to construct an empirical model of the EUV spectrum as a function of F10.7P= 1/2 (F-10.7+F(10.7)A) where F(10.7)A is the 81day average. We compare our spectra to the HEUVAC model and find the HEUVAC soft X-ray irradiance is approximate to 65% larger than SEE during solar minimum and HEUVAC H Lymann continuum fluxes are approximate to 30% smaller. We derive power law relationships between F10.7P and the ionizing irradiancethe integrated flux within some EUV wavelength bandin units of energy flux (F-E) and photon flux (F-P) for five neutral species and show that the relationship between F10.7P and F-E is more linear than that of F-P and that the magnitude of F-P and its solar cycle variation is species dependent. In addition, we derive power law relationships between F10.7P and the ionization frequencies of these species and confirm that F10.7P is a better EUV proxy than F-10.7. Finally, we investigate the hardening of the spectrum and its consequences for the Venus, Earth, and Mars ionospheres; the ratio of the soft X-ray to EUV irradiance appropriate for Earth's E and F layers stayed constant during the prolonged solar minimum. Our results can elucidate ionospheric processes such as the saturation effect.

• 出版日期2015-8