First Solar EUV Irradiances Obtained from SOHO by the CELIAS/SEM

Judge, D. L.; McMullin, D.; Ogawa, Hiromitsu; Hovestadt, D.; Klecker, B.; Hilchenbach, M.; Möbius, E.; Canfield, L. R.; Vest, Robert E.; Watts, R. N.; Tarrio, Charles S.; Kühne, M.; Würz, Peter

doi:10.1007/978-94-011-5000-2_12

Cited by 117 publications

(118 citation statements)

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“…GUVI also employs in-flight sensitivity tracking by periodic observations of known stellar fluxes, with estimated uncertainty of 10%, and its observations compare well with simultaneous dayglow observations by the Special Sensor Ultraviolet Spectral Imager (SSUSI) on the DMSP F-16 satellite. Furthermore, the solar cycle changes in SEE spectral irradiances converted to photon units and summed into two broadbands (0-45 nm and 28-34 nm) are generally consistent with independent measurements made by SEM on SOHO [Judge et al, 1998]. The assumed third component may therefore indicate a real source of solar variability in addition to the active regions and network contributions already encapsulated in the Mg II and F 10.7 indices, at least in this short wavelength spectral region.…”

Section: Irradiance Variability Amplitudessupporting

confidence: 82%

Solar extreme ultraviolet irradiance: Present, past, and future

et al. 2011

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[1] New models of solar extreme ultraviolet (EUV) irradiance variability are constructed in 1 nm bins from 0 to 120 nm using multiple regression of the Mg II and F 10.7 solar activity indices with irradiance observations made during the descending phase of cycle 23. The models have been used to reconstruct EUV spectra daily since 1950, annually since 1610, to forecast daily EUV irradiance and to estimate future levels in cycle 24. A two-component model developed by scaling the observed rotational modulation of the two solar indices underestimates the solar cycle changes that the Solar EUV Experiment (SEE) reports at wavelengths shorter than 40 nm and longer than 80 nm. A three-component model implemented by including an additional term derived from the smoothed Mg II index better reproduces the measurements at all wavelengths. The three-component model is consistent with variations in the EUV energy from 0 to 45 nm that produces the far ultraviolet (FUV) terrestrial dayglow observed by the Global Ultraviolet Imager (GUVI). However, the spectral structure of this third component is complex, and its origin is uncertain. Analogous two-and three-component models are also developed with absolute scales determined by the NRLEUV2 spectrum of the quiet Sun rather than by the SEE average spectrum. Assessment of the EUV absolute spectrum and variability of the four different models indicate that during solar cycle 23, the EUV irradiance (0 to 120 nm) increased 100 ± 30%, from 2.9 ± 0.2 to 5.8 ± 0.9 mWm −2 , and may have been as low as 1.9 ± 0.5 mWm −2 during the 17th-century Maunder Minimum. Near the peak of upcoming solar cycle 24, EUV irradiance is expected to increase 40% to 80% above the 2008 minimum values.

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Section: Irradiance Variability Amplitudessupporting

confidence: 82%

Solar extreme ultraviolet irradiance: Present, past, and future

et al. 2011

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“…A similar methodology has been applied to empirical models of transition height (Marinov et al, 2004;Kutiev and Marinov, 2007), vertical scale height in the top-side ionosphere (Kutiev et al, 2006) and TEC over Taiwan (Kakinami et al, 2009). Daily EUV (0.1-50 nm) measured by the Solar Heliospheric Observatory (SOHO) (Judge et al, 1998) and posted on the web site of the Space Science Center of the University of Southern California (http://www.usc.edu/dept/space science/), is used to construct the model. The released EUV fluxes are modified using the Sun-Earth distance because the released daily EUV fluxes are adjusted at 1 AU.…”

Section: Methodology Of the Construction Of An Empirical Modelmentioning

confidence: 99%

A comparison of a model using the FORMOSAT-3/COSMIC data with the IRI model

2012

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In this study, an empirical model constructed using data of FORMOSAT3/COSMIC (F3/C) from 29 June, 2006, to 17 October, 2009, retrieves altitude profiles of electron density (N e ). The model derives global N e profiles from 150 to 590 km altitude as functions of the solar EUV flux, day of year, local time and location under geomagnetically quiet conditions (K p < 4). N e profiles derived by the model are further compared with those of the International Reference Ionosphere (IRI). Results show that the F 2 peak altitude h m F 2 and the electron density N m F 2 , as well as the electron density above, derived by the model are lower than those of the IRI model. The F3/C model reproduces observations of F3/C well at 410-km altitude while the IRI model overestimates them. The overestimation of the IRI model becomes large with decrease of EUV flux. It is found that the topside vertical scale height of the F3/C model shows high values not only magnetic dip equator but also middle latitude. The results differ significantly from those of IRI, but agree with those observed by topside sounders, Alouette and ISIS satellites.

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“…The announced accuracy of TIMED/SEE measurements is 10-20% [Woods et al, 2005] and the accuracy of SOHO/SEM observations is ±14% [Judge et al, 1998]. A comparison of recent TIMED/SEE measurements of EUV with some empirical models [Woods et al, 2005, Figure 2.…”

Section: Observations and The Methods Of Analysismentioning

confidence: 99%

On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

Mikhailov

Perrone

2011

J. Geophys. Res.

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[1] Seasonal (winter/summer) and solar cycle N m F 2 variations as well as summer saturation effect in N m F 2 have been analyzed using Millstone Hill incoherent scatter radar (ISR) daytime observations. A self-consistent approach to the Ne(h) modeling has been applied to extract from ISR observations a consistent set of main aeronomic parameters and to estimate their quantitative contribution to the observed N m F 2 variations. The retrieved aeronomic parameters are independent of uncertainties in thermosphere and solar EUV empirical models, and this is a distinguishing feature of the present consideration. Different temperatures in winter and in summer in the course of solar cycle overlapped on the O + + N 2 reaction rate coefficient temperature dependence result in different N m F 2 dependences on solar activity: a steep practically linear increase with a tendency to turn up in January (contrary to international reference ionosphere prediction) and a slow increase with a tendency to saturate at high solar activity in July despite increasing solar EUV irradiation. In winter the EUV flux and thermospheric parameters provide approximately equal contributions to the N m F 2 increase, while in summer the contribution of thermospheric parameters is small. Both in winter and in summer the variations of atomic oxygen [O] are small at the F 2 layer peak, and its contribution is small compared to linear loss coefficient, b. It is shown that the summer saturation effect in N m F 2 under high solar activity is not just reduced to O/N 2 or EUV flux solar cycle variations but is determined by b via the g 1 temperature dependence. A new mechanism (qualitative) to explain the December anomaly in N m F 2 is proposed. It is based on the idea that the areas of atomic oxygen production and its loss are spatially separated and that time is required to transfer [O] from one area to the other where [O] associates in a three-body collision. Therefore, under a 7% increase in the O 2 dissociation rate due to the Sun-Earth distance decrease in December-January compared to June-July, an accumulation of atomic oxygen should take place in the thermosphere in the vicinity of the December solstice resulting in a 21% N m F 2 increase, which is close to the observed global December effect.Citation: Mikhailov, A. V., and L. Perrone (2011), On the mechanism of seasonal and solar cycle N m F 2 variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations,

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First Solar EUV Irradiances Obtained from SOHO by the CELIAS/SEM

Cited by 117 publications

References 12 publications

Solar extreme ultraviolet irradiance: Present, past, and future

Solar extreme ultraviolet irradiance: Present, past, and future

A comparison of a model using the FORMOSAT-3/COSMIC data with the IRI model

On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

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First Solar EUV Irradiances Obtained from SOHO by the CELIAS/SEM

Cited by 117 publications

References 12 publications

Solar extreme ultraviolet irradiance: Present, past, and future

Solar extreme ultraviolet irradiance: Present, past, and future

A comparison of a model using the FORMOSAT-3/COSMIC data with the IRI model

On the mechanism of seasonal and solar cycleNmF2variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations

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Product

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On the mechanism of seasonal and solar cycleN_mF₂variations: A quantitative estimate of the main parameters contribution using incoherent scatter radar observations