The Solar spectral irradiance at solar acivity minimum during the transi6on cycles 23 to 24*: A contribu6on to the PICARD- Climate program

Transcription

1 The Solar spectral irradiance at solar acivity minimum during the transi6on cycles 23 to 24*: A contribu6on to the PICARD- Climate program G. Thuillier 1, G. Schmidtke 2, S. Shapiro 3, D. Bolsée 4, W. Schmutz 3 B. Nikutowski 2 1 LATMOS, France 2 Fraunhofer Ins6tute, Germany 3 PMODWRC, Switzerland 4 Ins6tut d Aéronmie Spa6ale, Belgium * Accepted in Solar Physics

2 IMPORTANCE OF THE SOLAR MINIMUM OF Solar Spectral Irradiance (SSI) minimum is the base line of several reconstruc6ons SSI models. Furthermore, it is used for checking the accuracy of the SSI reconstruc6on, before running climate models in low solar ac6vity periods such as the Dalton minimum. - By comparing several SSI minima, the long term trend of the solar ac6vity can be studied. - The values of the different solar parameters at solar minimum (SSI, TSI, proxies,...) are essen6al to solar modelists to understand the cause of the minimum, in par6cular the recent 2008 minimum, lower that the others.

3 CYCLES 22 AND 23 MINIMA

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6 DATA USED IN THIS STUDY SolACES ON BOARD THE ISS. IT IS AN EUV SPECTROMETER SELF CALIBRATED USING GAS CELL. SSI IS MEASURED FROM 17 TO 150 NM. SOLSPEC ON BOARD THE ISS. IT IS A SPECTROMER MEASURING FROM 170 TO 2900 NM, USING ON BOARD LAMPS TO MAINTAIN THE STABILITY OF THE ABSOLUTE PHOTOMETRIC SCALE. BOTH INSTRUMENTS WERE CALIBRATED AT PTB (G). SOLSTICE ON BOARD SORCE.

7 OTHER SPECTRA and MODEL SPECTRA USED IN THIS STUDY SPECTRA: ATLAS 3 (Thuillier et al., 2004) Whole Heliospheric Interval (WHI, Woods et al., 2009) dated of 14 Feb EVE- SDO in prepara6on to SDO launch ( ) SCIAMACHY (Weber et al., 2010), (2002 in the IR part) SOLAR = SOLSPEC + SOLACES on board the ISS TSI: Theore6cal models: COSI (Shapiro et al., 2011) SRPM (Fontenla et al., 2011)

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9 White et al., 2011 show that TSI, F10.7 and Mg II are not in phase. Minimum in spring 2009

10 SolACES EUV MEASUREMENTS 21 November 2009 Photon flux is the integtrated SSI from 16 to 29 nm

11 SORCE- SIM λ = 215 nm 14 Feb. : WHI 26 June = Minimum at 215 nm 27 Feb. = Minimum Mg II Mg II 21 Aug = Minimum EUV Spring 2009 = Minimum TSI

12 DATES and Mg II INDEX, F10.7 RADIO FLUX and SUNSPOTS NUMBER Dates, sunspots number (SSN), F10.7 cm radio flux and Mg II index used in this ar6cle. For data covering several days, the mean values of the SSN, Mg II index and F10.7 solar radio flux is shown by < >.

13 1 SOLACES SSI SolACES (mwm -2 nm -1 ) July February August Wavelength (nm) SolACES SSI on 21 August is the lowest among these three dates. This is obtained by calcula6ng the SSI ra6o of 26/7/08 and 27/2/09 to 21/8/09 and comparing to the combined uncertainty of each spectrum.

14 0.5 ATLAS SolACES EVE SSI (mw/m2/nm) WHI Wavelength (nm)

15 SRPM SSI (mw/m 2 /nm) 200 SCIAMACHY ATLAS 3 COSI 100 SOLAR 1 WHI Wavelength (nm) SSI (mw/m 2 /nm) SRPM SCIAMACHY ATLAS 3 COSI 400 SOLAR WHI Wavelength (nm)

16 SSI (mw/m 2 /nm) SRPM SCIAMACHY ATLAS COSI SOLAR 1 0 WHI Wavelength (nm)

17 SOL = SOLAR- ISS; A3 = ATLAS 3 DATA SETS ACCURACY

18 ATLAS COSI SOLAR 1 SSI (mw/m 2 /nm) 400 SRPM WHI 200 SCIAMACHY Wavelength (nm)

19 DATA SETS ACCURACY

20 Brightness Temperature (K) SRPM COSI SOLAR-ISS SCIAMACHY ATLAS 3 WHI Wavelength (nm)

21 CONCLUSION We dispose of a spectrum at the lowest ac6vity observed during the transi6on between cycle 23 and cycle 24. WHI, SOLAR are in agreement taking into account their respec6ve accuracy. The smallest differences between the measurements and the theore6cal models are obtained with COSI. The missing opaci6es are likely the source of the differences. For past solar ac6vity studies, SSI at solar minimum is important to check the accuracy of the SSI reconstruc6ons, which usually are working less precisely at low than at high ac6vity. Climate studies are part of PICARD program using climate model and SSI reconstruc6ons of the past periods. These reconstruc6ons are necessary to run the climate model. The 2008 minimum will be useful to study the Dalton minimum period (in prepara6on). A reconstruc6on using the Mg II index and the 10 Be cosmogenic isotope concentra6on varia6on has been published (Thuillier et al, 2012, Solar Physics). The exis6ng reconstruc6ons have been compared (variability, absolute values) at different epochs to assess their agreement/ disagreement. It appears that by running the CMAN, the variability of the atmosphere hea6ng using these models is greater than the variability induced by the solar ac6vity effects predicted by each models (Thuillier et al., 2013, Solar Physics). Infered solar variability by modeling is in prepara6on.