Use of Simultaneous EUV and Soft X-ray Measurements for Diagnostics of the Solar Flare Radiation Danger     

L. A. Antonova  A. A. Nusinov 《Solar physics》1998,177(1-2):197-202

The fluxes of extreme ultraviolet (EUV) and soft X-ray emission are key parameters for modelling the ionosphere and upper atmosphere. A new aspect is considered in using these fluxes for diagnostics and short-term prediction of proton radiation danger from the flare. The EUV (λ < 105 nm) and soft X-ray (0.1–0.8 nm) fluxes were compared for two types of solar flares. The first type is followed by a strong enhancement in solar energetic (E >10 MeV) proton flux, the second is not followed by any enhancement in proton flux. It was discovered that the flare UV flux was considerably higher for flares with protons than for those without protons. Soft X-ray fluxes were approximately equal in both cases. An excess of EUV emission in proton flares grows with increasing proton flux. An analytic expression was found for the growth in proton flux as a function of the excess of EUV radiation at a given X-ray flux. These results can be used in predicting flare radiation danger.  相似文献   

Lyman-alpha line intensity as a solar activity index in the far ultraviolet range     

A. A. Nusinov  V. V. Katyushina 《Solar physics》1994,152(1):201-206

The relations between variations of far UV (FUV) emission in 115–210 nm waveband and L 121.6 nm and F_10.7 are studied. The changes of FUV flux are found to lag changes of F_10.7 - as a rule for 1 day. It is shown that such a difference may be caused by two factors: 1) differences between the rates of decrease of local sources' (active regions) brightness in FUV and 10.7 cm; 2) differences between limb-darkening curves for different wavelengths. One may expect the fluxes at different wavelengths to exhibit phase shifts of one relative to another. Cross-correlation analysis reveals no time-delay between emission fluxes within the FUV waveband, in spite of different laws for limb-brightening (darkening) for different spectral intervals. The absence of a phase delay can be caused by relatively small contribution of active regions to the flux of the whole Sun at these wavelengths. Thus the Lyman-alpha line intensity variation reflects variations of Solar FUV emission more precisely than F_10.7. Therefore, using the L intensity for flux intensity calculations of other FUV wavelengths is preferable to using the F_10.7 index.  相似文献   

Solar Radiation Fluxes in the 10–30 nm Range from Studying the E-region and E–F Valley     

A. A. Nusinov  L. A. Antonova  V. V. Katyushina 《Solar physics》1998,177(1-2):191-195

For the 10–30 nm interval within the extreme UV region of the solar spectrum, there are no commonly accepted views on the spectral composition and absolute magnitudes of the radiation intensity due to the lack of reliable data. This region is connected with characteristics of the ionosphere heat regime, photoelectron spectrum parameters and E–F valley characteristics. For estimating the solar radiation flux by the indirect route within the spectral region from 10 to 30 nm, which is difficult for direct measurements, it is suggested to use data on the electron concentration in the E-region maximum and E–F valley. Taken from empirical models, the data on these parameters were correlated with theoretical calculations of height profiles of electron concentration in the ionosphere. Based on the proportion between electron concentration in the E-layer maximum and E–F valley minimum, the solar radiation flux within the 10–30 nm region was shown to be 2.5 times greater than that obtained in measurements on board the ‘AE–E’ and ‘AE–C’ satellites. The results are used for correcting model spectra of the extreme UV radiation.  相似文献   

Hysteresis of indices of solar and ionospheric activity during 11-year cycles     

E. A. Bruevich  T. V. Kazachevskaya  V. V. Katyushina  A. A. Nusinov  G. V. Yakunina 《Geomagnetism and Aeronomy》2016,56(8):1075-1081

The effects of hysteresis, which is a manifestation of ambiguous relationships between different solar activity indices during the rising and declining phases of solar cycles, are analyzed. The paper addresses the indices characterizing radiation from the solar photosphere, chromosphere, and corona, and the ionospheric indices. The 21st, 22nd, and 23rd solar cycles, which significantly differ from each other in amplitude, exhibit different extents of hysteresis.  相似文献   

Limitation of the accuracy of F2-layer critical frequency predictions due to variations in the flux of the Sun’s extreme UV radiation     

A. A. Nusinov  T. V. Kazachevskaya 《Geomagnetism and Aeronomy》2013,53(3):356-361

The accuracy limitations of critical frequency predictions in the ionospheric F2 layer are considered, which arise due to random variations in the Sun’s extreme UV radiation during the month. An analysis of δf (relative values of monthly rms scatters of the F2-layer critical frequencies) and the appropriate δu values (monthly rms scatters of extreme UV radiation) has shown their dependence on the solar activity level. A conclusion is drawn that when prognostic models of monthly medians are used for forecasting foF2 for a particular date, the error can hardly be less than ～7% at low solar activity and ～15% at a higher solar activity level.  相似文献