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

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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

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

Margit Haberreiter

Juan Fontenla

LASP, University of Colorado

Boulder, USA

motivation
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
euv spectrum
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
atmosphere structures chromosphere
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

slide6
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
spherical symmetry
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

eve rocket flight
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)
euv irradiance spectra
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
euv radiance spectra of quiet sun
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.)
masks of active regions
Masks of active regions

Solar maximum: September 22, 2001

Solar minimum: April 10, 2008

conclusions
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
future plans
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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