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Published byLetizia Mauro Modified over 6 years ago
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The EUV spectral irradiance of the Sun from 1997 to date
Giulio Del Zanna PPARC/STFC Adv. Fellow DAMTP, CMS, University of Cambridge Vincenzo Andretta OAC INAF, Italy Tom Woods, Phil Chamberlin et al., LASP, Univ. of Colorado, USA (Del Zanna et al. 2005,2006, 2009)
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G. Del Zanna - UKSP/NAM/JENAM 2009
Key questions What is the EUV spectral irradiance and how it varies? Can we model it ? Does it affect our climate? The total irradiance is one of the main drivers for global climate. Variability exists but is small (0.2%) and insufficient to explain variations on global weather. EUV -- 1 MK X-ray MK "Winter Scene with Frozen Canal" by Aert van der Neer SOHO TRACE Yohkoh G. Del Zanna - UKSP/NAM/JENAM 2009
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CALIBRATION CALIBRATION CALIBRATION
Why study UV and EUV ? UV radiation could be a significant driver for terrestrial climate (e.g. Haigh 1996). The EUV radiation creates the ionosphere and might also have an indirect effect. Spectral irradiance measurements: plenty in UV, almost none in X-rays and EUV (until TIMED 2002) EUV irradiances NASA TIMED/SEE UV irradiances CALIBRATION CALIBRATION CALIBRATION Source: LASP, Univ. of Colorado) G. Del Zanna - UKSP/NAM/JENAM 2009 Woods & Eparvier (2006)
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G. Del Zanna - UKSP/NAM/JENAM 2009
CDS NIS G. Del Zanna - UKSP/NAM/JENAM 2009
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SOHO CDS NIS: 1000 exposures sampling the whole Sun in 13 hours
He I, O V (0.25), Mg X (1 MK), Fe XVI (2.5 MK) `Del Zanna minimum’ ? G. Del Zanna - UKSP/NAM/JENAM 2009
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SDO EVE prototype ‘It could take a lifetime to understand such a spectrum’ (P.J.Storey, UCL) Woods et al. (GRL, 2009) Chamberlin et al. (GRL, 2009) G. Del Zanna - UKSP/NAM/JENAM 2009
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SOHO NIS irradiances vs. EVE prototype
SDO/EVE G. Del Zanna - UKSP/NAM/JENAM 2009
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G. Del Zanna - UKSP/NAM/JENAM 2009
CDS NIS irradiances G. Del Zanna - UKSP/NAM/JENAM 2009
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Summary and further work SDO EVE vs. NIS radiances
The irradiances in lines formed in the low transition region have changed little (max 50%) over the last 12 years (also from late 60’s). At 1 MK by a factor of 5 and at 2.5 MK by a factor of 40. Further work: Explain the Sun-as-a-Star and other stars in XUV with radiance measurements. Improve predictions of EUV radiances and irradiances (current models use proxies: does not work!): - climate models - back in time. thank you B2/ G. Del Zanna - UKSP/NAM/JENAM 2009
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