Measurements of the solar soft X‐ray irradiance by the Student Nitric Oxide Explorer: First analysis and underflight calibrations

Bailey, S. M.; Woods, T. N.; Barth, C. A.; Solomon, Stanley C.; Canfield, L. R.; Korde, R.

doi:10.1029/2000ja000188

Cited by 80 publications

(82 citation statements)

References 33 publications

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“…The SNOE-SXP irradiance data are no exception (see Fig. 7 of Bailey et al 2000), showing correlation coefficients of %0.9 (see Table 1). The second data set is the irradiance of the C iv 1548, 1550 doublet observed with the SOLSTICE instrument on the Upper Atmosphere Research Satellite since 1991, for which accurate daily values are available (T. Woods 2002, private communication).…”

Section: Extrapolationsmentioning

confidence: 99%

“…The SNOE-SXP instrument and its performance are described by Bailey et al (2000). In brief, the instrument consists of three silicon diodes sensitive in the soft X-ray to extreme-ultraviolet wavelength range (XUV), with different filter materials deposited directly on the diode surfaces.…”

Section: Snoe-sxpmentioning

confidence: 99%

“…Placing solar X-rays accurately in the context of stars can in principle tell us a great deal about magnetic activity, extending beyond what is possible by studying the Sun or stars separately. Here we relate solar coronal emissions to the stars using data from the Solar X-Ray Photometer (SXP) instrument on board the Student Nitric Oxide Explorer (SNOE) satellite (Bailey et al 2000) and archival data from the Position Sensitive Proportional Counter (PSPC) instrument on the ROSAT satellite. Our aim is to place the mean coronal activity level, and the rotational and cyclic variations, of the Sun firmly among the stellar database obtained by ROSAT-PSPC.…”

Section: Introductionmentioning

confidence: 99%

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An Estimate of the Sun’sROSAT‐PSPC X‐Ray Luminosities UsingSNOE‐SXP Measurements

Judge

Solomon

Ayres

2003

ApJ

119

118

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Using solar soft X-ray irradiance measurements from the SXP instrument on the SNOE satellite, we relate the solar surface flux densities and their variability to those of stars as measured with the PSPC instrument on ROSAT. We translate SNOE-SXP measurements into equivalent ROSAT-PSPC counts using model spectra calculated from the CHIANTI package. Using the SNOE-SXP measurements has significant advantages over earlier studies: the absolute calibration is known to AE25%, SNOE measures the Sun as if it were an unresolved star, it has operated over a significant fraction of the solar cycle, and its three wavelength channels overlap substantially with that of the ROSAT-PSPC instrument. The predicted solar X-ray luminosities and surface flux densities are compared with measurements from the ROSAT database. We find that we can estimate the luminosity of the Sun as seen in the 0.1-2.4 keV ('' RASS '') passband of ROSAT-PSPC to within AE50%, not counting sources of systematic uncertainty mentioned in an appendix: the result lies between 10 27:1 and 10 27:75 ergs s À1 (measured in the existing data set, only partially covering a full solar cycle) and between 10 26:8 and 10 27:9 ergs s À1 (extrapolated to the full activity range of a typical solar cycle). The solar luminosities lie close to the median behavior found for a volume-limited (d < 13 pc) sample of G stars studied in 1997 by Schmitt, revealing the Sun to be a normal or slightly inactive G dwarf. A factor of 1.5 peak-to-peak variation in the RASS passband is predicted due simply to rotational modulations (i.e., those filtered to include periods P < 81 days). The ratio of maximum/minimum RASS luminosities from the magnetic activity cycle (filtered to include periods P > 81 days) are estimated to be 0.7-0.8 in log 10 L RASS , a ratio of 5 or 6. These variations are much smaller than both recent estimates of solar X-ray variability and the range of X-ray luminosities seen within Schmitt's sample. It is suggested that the reported absence of '' solar-like '' cyclic emission in stellar X-rays might partly arise because the Sun is less variable than assumed in some earlier work. Repeated ROSAT observations of Cen A during 1995-1998 show X-ray behavior reminiscent of the Sun during activity minimum conditions.

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Section: Extrapolationsmentioning

confidence: 99%

Section: Snoe-sxpmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An Estimate of the Sun’sROSAT‐PSPC X‐Ray Luminosities UsingSNOE‐SXP Measurements

Judge

Solomon

Ayres

2003

ApJ

119

118

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“…It is evident that the irradiance can vary by 5 orders of magnitude or more. The upper-atmospheric effects of X-ray absorption during solar flares have been studied by satellites such as TIMED (Woods et al, 2002) and the Student Nitric Oxide Explorer (SNOE), (Bailey et al, 2000). The effects can also readily be monitored remotely by ground-based instruments.…”

Section: Introductionmentioning

confidence: 99%

Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

et al. 2008

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Abstract. Two case studies of upper mesospheric and lower thermospheric (UMLT) high-latitude effects of solar X-ray flares are presented. Sodankylä Ion-neutral Chemistry Model (SIC) electron density profiles agree with D-region EISCAT and riometer observations, provided that the profiles of the most variable ionisable component, nitric oxide, are adjusted to compensate for NO x production during preceding geomagnetically active periods. For the M6-class flare of 27 April 2006, following a quiet period, the agreement with cosmic noise absorption observed by the Sodankylä riometers was within reasonable limits without adjustment of the [NO] profile. For the major (X17-class) event of 28 October 2003, following high auroral activity and solar proton events, the NO concentration had to be increased up to on the order of 10 8 cm −3 at the D-region minimum. Thus [NO] can in principle be measured by combining SIC with observations, if the solar spectral irradiance and particle precipitation are adequately known.As the two case events were short and modelled for high latitudes, the resulting neutral chemical changes are insignificant. However, changes in the model ion chemistry occur, including enhancements of water cluster ions.

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“…These differences are conveniently expressed in terms of recommended scalings of irradiances below $20 nm from the Hinteregger et al [1981] (HFG) model. Scalings of $2 and $4 have been recommended by Richards and Torr [1984] and Bailey et al [2000], respectively. However, a model of EUV spectral irradiance variability, NRLEUV, constructed from the physical properties of the emitting regions in the solar outer atmosphere and with many more emission lines than the HFG model, suggests a lower scaling, of only 40% during solar minima [Warren et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

Solar EUV irradiance variability derived from terrestrial far ultraviolet dayglow observations

Strickland

Lean

Meier

et al. 2004

Geophysical Research Letters

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[1] Remotely sensed ultraviolet emissions from the Earth's upper atmosphere are shown to mirror fluctuations in solar EUV irradiance during July 2002, including the overall increase and decrease as the Sun rotated, and episodic increases associated with multiple solar flares. The TIMED/ GUVI dayglow observations are used to derive a new quantity, Q EUV GUVI , which is a measure of integrated solar EUV electromagnetic energy shortward of 45 nm. Both the absolute Q EUV GUVI values and their modulation by solar rotation agree well with the corresponding solar EUV energy estimated by the NRLEUV irradiance variability model. The Q EUV GUVI values do not support recent suggestions that the solar EUV irradiances estimated by the model of Hinteregger et al. be increased by a factor of four, nor even a factor of two.

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Measurements of the solar soft X‐ray irradiance by the Student Nitric Oxide Explorer: First analysis and underflight calibrations

Cited by 80 publications

References 33 publications

An Estimate of the Sun’sROSAT‐PSPC X‐Ray Luminosities UsingSNOE‐SXP Measurements

An Estimate of the Sun’sROSAT‐PSPC X‐Ray Luminosities UsingSNOE‐SXP Measurements

Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

Solar EUV irradiance variability derived from terrestrial far ultraviolet dayglow observations

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