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Retrieving the EUV solar spectrum from a selected set of lines for space weather purposes: A review of theories, models and experiments J. Lilensten, T. Dudok de Wit, M. Kretzschmar, P.-O. Amblard, S. Moussaoui, J. Aboudarham and F. Auchère (ias). Wavelength.

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Importance of EUV flux for space weather purposes

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Importance of euv flux for space weather purposes

Retrieving the EUV solar spectrum from a selected set of lines for space weather purposes: A review of theories, models and experiments

J. Lilensten, T. Dudok de Wit, M. Kretzschmar, P.-O. Amblard, S. Moussaoui, J. Aboudarham and F. Auchère (ias)

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Wavelength

  • Importance of EUV flux for space weather purposes

  • Influences the near space environment (ionosphere / thermosphere)

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  • Result (amongst other phenomena) in

  • Dilatation of the thermosphere (density may increase by a factor of 10 at the altitude of the International Space Station)

  • rapid variations, creations of small scale disturbances, winds

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Variations are not linear

Pap and Frölich, 1999; Nesme-Ribes and Thuiller, 2000

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Their characteristic variation times range from the second to several years

14 July 1998

27 days

CELIAS/SEM experiment, Bochsler, 1999

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  • 2) Existing models for Aeronomy

    • . Poorly sampled and / or based on too short data sets (2 years with TIMED)

F79050, f10.7 = 243

SC#21REF, f10.7 = 70

C++

O5+

He

O4+

Mg10+

O3+

O5+

O++

Ne6+

He+ et Si9+

Lyman b

Fe14+

N3+et Ne7+

O3+etMg9+

Si10+ et He+

Torr and Torr (1985)

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

SERF / HFG

Torr, M.R., and D.J. Torr, J. Geophys. Res.90, 6675-6678, 1985

EUV / SOLAR 2000

Tobiska, W. K. and F. Eparvier, Sol. Phys., 177, 147-159, 1998

EUVAC / HEUVAC

Richards, P. G., J. A. Fennelly, and D.J. Torr, J. Geophys. Res.99, 8981-8992, 1994

P. G. Richards, T. N. Woods, and W. K. Peterson, Adv. Spa. Res., 37, 315-322,2006

NRLEUV

Lean et al, J. Geophys. Res.108, 1059, 2003

Warren et al., J. Geophys. Res.106, 15 745, 2001

Other:

Nusinov A. A., models for prediction of EUV and W-ray solar radiation based on 10.7 cm radio emission, Ed. R.F. Donnely, NOAA ERL, 1992

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Year

  • 2) Existing models for Aeronomy

    • . Based on indices (Ri, f10.7, Mg …) or proxies (E10.7, X10.7, Iu …)

    • (see poster P2.7, Menvielle)

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  • 2) Existing models for Aeronomy

    • . The proxies are NOT well correlated to the solar activity

    • See poster P3.14, Dudok de Wit et al.

T. Dudok de Witet al., Which solar EUV proxies are best for reconstructing the solar EUV irradiance?,submitted to Adv. Spac. Res., 2006

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  • 3) To measure the full spectrum ?

    • . Difficult and expensive

Schmidtke et al., Tiger program, Adv. Sp. Res., 10, 1553-1559, 2002

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Today : only Solar Extreme Ultraviolet Experiment (SEE) onboard TIMED (NASA)

  • EUV Grating Spectrograph (EGS)

    • 25 à 200 nm

    • 0.4 nm spectral resolution.

EGS

  • XUV Photometer System (XPS)

    • 0.1 to 35 nm in 12 spectral bands

XPS

Woods, et al., Solar EUV Experiment (SEE): mission overview and first results. J. Geophys. Res., 110, 1312-1336, 2005.

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  •  Several attempts to retrieve the full spectrum

  • Retrieve the flux variation through their effects

  • On electron density profiles (Mikhailov and Schlegel, Ann. Geoph., 18, 1164 – 1171, 2000)

  • On the E region critical frequency (Nusinov, Adv. Space Res., 37, 426-432, 2006)

  • On the thermospheric emission (Singh and Tyagi, Adv. Space Res., 30, 255è-2562, 2002)

  • On wind or temperatures (Zhang et al., Geoph. Res. Lett., 29, 10.029/2001GL013579, 2002)

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

  • These method depend all on a given model:

  • They cannot be general

  • They cannot be used as operationnal tools

  • They are absolutely required for tests

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Reduce the solar spectrum to a limited (3) set of characteristic spectra: very promissing method through positive source separation

SEE (TIMED) : reconstruction < 2%

Quiet sun contribution?

Active zone contribution?

Hot lines contribution?

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Physics through Differential Emission Measure: 6 to 10 lines are necessary

See poster P6.4, Kretzschmar et al.

M. Kretzschmar et al., Retrieving the Whole Solar EUV Flux from 6 Irradiance Line Measurements, Advances in Space Research, 37, 341–346, 2006

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Use statistics (Singular Value Decomposition): 6 to 10 lines are necessary. Same conclusion through 2 totally different approaches

T. Dudok de Wit, et al., Retrieving the solar EUV spectrum from a reduced set of spectral lines, Annales Geophysicae, 23, 3055–3069, 2005

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

How to choose the lines to be observed?

Statistical analysis of TIMED/SEE data.

Using two

years of daily EUV spectra and classification techniques,

Dendrogram of 38 spectral lines using an average distance

linkage between all lines.

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

This table allows to select the best set of lines to observe in order to reconstruct the total flux with the best accuracy.

The relative global error for the best combination of 6 lines yields to 3.7% and less than 0.25% with 10 lines

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

However, the « best » set may depend on the application. An example : the ionosphere

How to choose an observed set of solar lines for aeronomy driven applications, J. Lilensten et al., submitted to Ann. Geoph., 2006

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Using a multidimensional scaling technique :

H I at 102.572 nmCIII at 97.702 nmOV at 62.973 nmHeI at 58.433 nmFeXV at 28.415 nmHeII at 30.378 nm

Allows to retrieve the full solar spectrum with a relative global error of 6.8 % and still fulfill ionospheric physics requirements.

ESWW4, Brussels, Novembre 2006


Importance of euv flux for space weather purposes

Near future: LYRA, the Solar VUV radiometer on-board PROBA II

J.-F. Hochedez et al., Adv. Space Res., 37, Iss 2, 303-312, 2006

http://lyra.oma.be/index.php

1/ Lyman-alpha (115-125 nm)

2/ the 200-220 nm range

3/ Al filter channels (17-70 nm

4/ MgF2 windows (120-220 nm),

And EVE on-board SDO

http://lasp.colorado.edu/eve/eve_home.html

ESWW4, Brussels, Novembre 2006


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