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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



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


Fe ix 17 1 nm disk integrated plane parallel vs spherical
Fe IX 17.1 nm - disk integrated Plane parallel vs. spherical


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 continuumquiet 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 continuum

Solar maximum: September 22, 2001

Solar minimum: April 10, 2008



Conclusions
Conclusions continuum

  • 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 continuumplans

  • 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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