Modeling the UV/EUV and its relevance for PROBA2 observations Margit Haberreiter Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center, Davos, Switzerland and Laboratory for Atmospheric and Space Physics, University of Colorado, USA

EUV spectrum Wavelengths –UV: 120 – 400 nm –EUV: 10 – 120 nm Contribution from the –Chromophere –Transition region –Corona

Solar Modeling (SolMod – continuation of SRPM) Multi level atoms –373 ions, from H to Ni with ioncharge 25 –~14’000 atomic levels –~170’000 spectral lines –Statistical equation is solved to get the level populations Chromosphere and transition region –for ioncharge  2: –full NLTE ( Fontenla et al., 2006; 2007; 2009) –plus optically thin transition region lines –Spherical symmetry Corona –ioncharge >2 –optically thin, i.e. collisions and spontaneous emission –Line of sight integration accounts for opacity –Spherical symmetry

Masks from Precision Solar Photometric Telescope Disk mask on 2005/9/12 obtained from PSPT data, Mauna Loa, Hawaii (R) Sunspot Penumbra (S) Sunspot Umbra (P) Faculae (H) Plage (F) Active network (D) Quiet network (white) (B) Intergranular Cells Determined by the contrast as a function of the position on the disk -Only possible with respect to a -normalized quiet Sun intensity Continuum, 607 nm (PICARD) Ca II 393.4, FWHM=0.27nm

Faculae Plage Active network Quiet network Intergranular Cells Fontenla et al., 2009, ApJ 707,

G-Band of CH molecular lines Fontenla et al., 2009, ApJ 707,

Violet CN Band Fontenla et al., 2009, ApJ 707,

Fontenla, Curdt, Haberreiter, et al., 2009, ApJ

Modeling the EUV e.g. Fe XV 284 Å

Coronal models SRPM Models are based on Doschek (1997), ApJ, 476, 903, Singh et al., 1982, J. Astrophys. 3, 249 Cranmer et al, 2007, ApJS 171, 520

Coronal lines and Bremsstrahlung

Spectrum from Corona, TR and Chromosphere

SPRM calculation versus the EVE spectrum

EVE calibration spectrum versus calculated spectrum Haberreiter and Fontenla, 2009, AIP conference series EVE rocket calibration flight: Chamberlin et al., 2009, GRL

Quiet Sun versus Coronal Hole

Spherical Symmetry Allows the calculation of intensities at and beyond the limb (e.g. Haberreiter et al. 2008) Account for corona over 2 x area of solar disk Adopted from Mihalas, 1978

Spherical symmetry

Spherical geometry EIT 171 Å

SOHO/EIT images He II 30.4 nm Fe XV 28.4 nm Fe IX 17.1 nm Fe XII 19.5 nm

EIT wavelengths EVE spectrum SRPM calculation

EIT passbands Fe IX 17.1 nm Fe XII 19.5 nm Fe XV 28.4 nm He II 30.4 nm

He II 30.4 nm – high resolution

Optical depth Fe XV 17.1 nm: –Disk center:  max = 0.06 –Limb: (r=1.02):  max = 0.63 (~900,000K) Fe XV 19.5 nm: –Disk center:  max = 0.06 –Limb: (r=1.02):  max = 0.34 (~1,100,000K) Fe XV 28.4 nm: –Disk center:  max = 0.39 –Limb: (r=1.02):  max = 0.88 (~2,000,000K)

LYRA passbands LYRA CH 3: nm LYRA CH 4: 6-20 nm

LYRA measure- ments April 2010 Courtesy, Ingolf Dammaschs

LYRA measure- ments May 2010 Courtesy, Ingolf Dammaschs

Understand the daily variations of the UV/EUV Determine the solar cycle variation of solar activity features (with an emphasis on coronal holes) → create masks similar to PSPT masks Model the variation of the solar spectrum in the EUV Is there a long-term trend of the solar spectral irradiance (due to coronal holes)

Questions to address Understand the spectral variability Do all the spectral lines behave similarly OR Increase of line strength of some lines and a decrease of others? Is a decrease in the EUV responsible for the decrease in TSI for the current minimum

1. Variability of solar activity features EIT 17.1nm 07/01/2005 EIT 19.5 nm 10/01/2002 EIT 28.4 nm 10/10/2003 EIT 30.4 nm 07/10/2006 coronal holes – quiet Sun – quiet coronal network – active coronal network - hot loop – super hot loop

EIT image analysis Radial dependence for outer corona Thresholds based on intenstiy histogram of the EIT images Maximum value of histogram varies with solar cycle (in particular for 284 Ǻ) Coronal hole intensity changes with solar cycle – (Barra et al., 2009) → identification of coroanl features not trivial

Area coverage of features Data from Barra et al, 2009

3. Determine the long-term trend of the solar spectral irradiance The SOHO/SEM measurements indicate a decrease in the EUV by15% Uncertainty ~ 6% Not explained by F10.7 or sunspot number What is the role of coronal holes? Didkovsky et al., 2009

Conclusions Good agreement between the synthetic spectra and the observed EVE quiet Sun spectrum An enourmous amount of spectral lines is contained in broader spectral bands Strong interest in SWAP images for the reconstruction of LYRA observations

Questions?