Finding the best proxies for the solar UV irradiance

Wit, T. Dudok de; Kretzschmar, M.; Lilensten, Jean; Woods, T. N.

doi:10.1029/2009gl037825

Cited by 84 publications

(69 citation statements)

References 29 publications

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“…The index is the ratio of the emission in the core of the (unresolved) lines to that in the nearby photospheric continuum. Comparisons of the Mg II index with other chromospheric indices verify its utility as a stable indicator of the variability of the solar chromosphere ] and a useful proxy for EUV irradiance variations [Viereck et al, 2001;Dudok de Wit et al, 2009]. Since the magnitude of the Mg II index depends on the spectral resolution of the measurements, different data sets must be carefully cross-calibrated during periods of overlap.…”

Section: Observed Irradiance Variationsmentioning

confidence: 87%

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: Observed Irradiance Variationsmentioning

confidence: 87%

Solar extreme ultraviolet irradiance: Present, past, and future

et al. 2011

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“…Dudok de Wit et al (2009) andBruinsma (2011) have shown that no single proxy can properly reproduce the UV variability at all time scales. Let us therefore build a more global picture and compare our different quantities scale-wise.…”

Section: Comparison With Solar Proxiesmentioning

confidence: 99%

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Wit

Bruinsma²

2017

J. Space Weather Space Clim.

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The 10.7 cm radio flux (F10.7) is widely used as a proxy for solar UV forcing of the upper atmosphere. However, radio emissions at other centimetric wavelengths have been routinely monitored since the 1950 s, thereby offering prospects for building proxies that may be better tailored to space weather needs. Here we advocate the 30 cm flux (F30) as a proxy that is more sensitive than F10.7 to longer wavelengths in the UV and show that it improves the response of the thermospheric density to solar forcing, as modelled with DTM (Drag Temperature Model). In particular, the model bias drops on average by 0-20% when replacing F10.7 by F30; it is also more stable (the standard deviation of the bias is 15-40% smaller) and the density variation at the the solar rotation period is reproduced with a 35-50% smaller error. We compare F30 to other solar proxies and discuss its assets and limitations.

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“…Missing observations can be filled via different statistical methods using solar proxies. However, it has been shown that none of the current solar proxies can properly reconstruct the solar UV irradiance on all timescales (Dudok de Wit et al 2009), making direct observations of the UV irradiance mandatory for all space weather applications (Lilensten et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Solar irradiance observations with PREMOS filter radiometers on the PICARD mission: In-flight performance and data release

Cessateur

Schmutz

Wehrli

et al. 2016

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Context. The PREcision Monitoring Sensor (PREMOS) is a solar radiometer on board the French PICARD mission that was launched in June 2010 and decommissioned in April 2014. Aims. The PREMOS radiometer obtains solar irradiance measurements in specific spectral windows in the UV, visible, and nearinfrared. In this paper, the PREMOS data and calibration methods are presented. Methods. Using back-up channels, the degradation can theoretically be assessed to correct operational channels. However, a strong degradation within all PREMOS channels requires the application of additional methods, namely using back-up channels and assessing the degradation via a proxy-based model. Results. The corrected Level 3 PREMOS data are then used in different contexts in order to be validated. First, the signature of the p-mode are retrieved from the PREMOS data. The Venus transit allows us to empirically determine the intrinsic noise level within the PREMOS high cadence data for the visible and near-infrared channels. We then compare the PREMOS data directly to other data sets, namely from the SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) and the Solar Irradiance Monitor (SIM) instruments on board the SOlar Radiation and Climate Experiment (SORCE) spacecraft. Regarding the UV channels, we found an excellent correlation over the lifetime of the PREMOS mission. The ratio between SORCE and PREMOS observations is always less than 1%. Regarding the SSI measurements in the visible and near-infrared, a comparison of short-term variations (i.e. 27-day modulation) shows a rather good correlation by taking into consideration the intrinsic noise within both SIM and PREMOS observations.

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Finding the best proxies for the solar UV irradiance

Cited by 84 publications

References 29 publications

Solar extreme ultraviolet irradiance: Present, past, and future

Solar extreme ultraviolet irradiance: Present, past, and future

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Solar irradiance observations with PREMOS filter radiometers on the PICARD mission: In-flight performance and data release

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