The absolute solar soft X ray flux in the 20‐ to 100‐Å region

Abstract

In the present work we have used the best available solar spectral data together with our absolute neon ionization cell data to estimate the absolute solar soft X ray flux and its variation with solar activity in the 20‐ to 100‐Å region. Since the neon chamber data cover the integral spectral region from 20 to 575 Å we have constructed a composite spectrum covering that region so that the fraction of solar flux in the 20‐ to 100‐Å region could be determined. Both sounding rocket and satellite observations obtained over the past two decades have been used in the present analysis. Most of these prior data were acquired during low and moderate solar activity levels in contrast with the neon ionization cell data which were obtained during moderate and maximum solar activity levels. Based on these combined data sets we have shown the dependence of the integrated solar soft X ray flux between 20 and 100 Å on the daily 10.7 cm radio flux observed at 1 AU and have obtained an estimate of the maximum flux that can be expected over the solar cycle.

A comparison of models of the Sun's extreme ultraviolet irradiance variations

“…Measurements made prior to 1980 have been reviewed in detail by Lean [ 1987Lean [ , 1988a. Rocket measurements of the total EUV flux in broad wavelength intervals have also been made [Ogawa and Judge, 1986;Feng et al, 1989] but are not addressed here because of their lack of spectral resolution. The data products of the AE-E instruments, adopted for use by the aeronomy community, are a reference spectrum for minimum solar activity (SC#21REFW) and daily ratios to the solar minimum irradiance of EUV emissions in selected wavelength intervals, during the ascending phase of solar cycle 21 (SC#210BS).…”

Effect of solar soft X‐rays on the lower ionosphere

“…They deposit their energy throughout the thermosphere, but especially in the altitude range from 100 to 200 kin. Broad-band ionization cell and photodiode measurements [Feng et al, 1989;Ogawa et al, 1990;Bailey et al, 1999a] Other evidence points in the same direction, including airglow analyses, calculation of nitric oxide densities, and modeling of the lower ionosphere. Work by Buonsanto et a/.…”

Solar photoionization as a loss mechanism of neutral interstellar hydrogen in interplanetary space

“…The similarity of the magnitudes of the solar EUV radiation during the two solar cycles is illustrated in Figures 3 and 4 3 and 4, 1969); however, neither data set covers the full ionizing wavelength region of hydrogen. We therefore have adjusted the absolute fluxes according to Feng et al [1989] and have accordingly projected the photoionization rates for 1969 assuming that the relative spectral distribution of the two data sets are similar to the solar maximum flux distribution of Tort and Tort [1985]. The results of these calculations are presented in Table 3.…”