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VI. Forecasting Solar EUV/UV Radiation – EUV spectral synthesis

VI. Forecasting Solar EUV/UV Radiation – EUV spectral synthesis. Margit Haberreiter Juan Fontenla LASP, University of Colorado Boulder, USA. Motivation. EUV/UV influences the neutral density in the thermosphere/ionosphere Influence on satallite drag

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VI. Forecasting Solar EUV/UV Radiation – EUV spectral synthesis

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  1. VI.Forecasting Solar EUV/UV Radiation – EUV spectral synthesis Margit Haberreiter Juan Fontenla LASP, University of Colorado Boulder, USA

  2. Motivation • EUV/UV influences the neutral density in the thermosphere/ionosphere • Influence on satallite drag • Aim: forecast the EUV radiation based on physical principles over a solar rotation • Focus: physics-based EUV spectral synthesis

  3. EUV spectrum • Contribution from • chromophere • transition region • corona • Input to our model: • temperature and density structures of each of these regimes for various regions on the solar disk

  4. Atmosphere structures – chromosphere Upper chromosphere Lower chromosphere Quiet Sun Quiet Netw. Active Netw. Plage Faculae Semi-empirical NLTE structures reproduce radiance observations at 1-2‘‘(Fontenla et al 2008, in prep.) The models describes the distribution of heated areas on solar disk

  5. Coronal models

  6. SRPM • Multi level atoms • 373 ions,from neutral H to Ni with ioncharge 25 • ~14’000 atomic levels • ~170’000spectral lines • Chromosphere and transition region: • for ioncharge up to 2: • full NLTE (Fontenla et al., 1999; 2006; 2007) • plus optically thin transition region lines • Corona • ioncharge >2: optically thin, i.e. collisions and spontaneous emission

  7. Extension of Corona

  8. Spherical Symmetry Spherical symmetrie: Calculation of intensities at and beyond the limb In total: 2 x area of solar disk Plane parallel: Only disk rays are calculated

  9. Fe IX 17.1 nm - disk integrated Plane parallel vs. spherical

  10. EVE rocket flight • Calibration flight on April 10, 2008 at “Solar minimum“ conditions (EVE rocket team at LASP: Tom Woods, Frank Evapier, Phil Chamberlin, Rahel Hock, a.o., Chamberlin et al., in preparation)

  11. EUV irradiance spectra

  12. EUV irradiance spectra • 0.75 Quiet Sun (B) +0.22 (Quiet Network) +0.03 Active Network (F) • Lyman continuum matches well with EVE rocket spectrum from April 10, 2008

  13. EUV irradiance spectra at instrument resolution

  14. Shorter than 50 nm coronal/upper TR lines form a pseudo continuum

  15. EUV Irradiance QS 10-40 nm

  16. EUV radiance spectra of quiet Sun • 0.75 Quiet Sun (B) +0.22 (Quiet Network) +0.03 Active Network (F) • Good agreement with average QS (SUMER Atlas, Curdt et al.)

  17. Masks of active regions Solar maximum: September 22, 2001 Solar minimum: April 10, 2008

  18. EUV spectrum Active Sun

  19. Conclusions • The vast number of spectral lines have to be included • Due to the extension of the corona spherical symmetry is essential for coronal lines • SRPM EUV spectra agree well with EVE rocket irradiance spectrum and SUMER radiance spectra

  20. Future plans • Validation against more EUV observations • include coronal holes and active region loops in the calculation of the spectrum • Produce daily EUV/UV spectra • changing distribution of coronal features, e.g. coronal holes, active region loops • Apply the forcasting scheme as shown before

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