Synergies between solar UV radiometry and imaging

J.-F. Hochedez, COSPAR ’06, Beijing

Synergies between solar UV radiometry and imaging

Matthieu Kretzschmar ° Jean-François Hochedez °Véronique Delouille °Vincent Barra *Thierry Dudok de Witte ‘

° Royal Observatory of Belgium, Brussels* ISIMA, Clermont-Ferrand, France‘ LPCE, Orléans, France


A metaphor about multi-dimensionality

A snake !

A wall !

A curtain !Dr Elephant


Dimensions of (solar UV) observations

Spatial resolution

Field of ViewCadence

Exposure time

Temporal coverage(Long-term and duty cycle)

Spectral range & resolution +polarimetric diagnostics

Effective area, calibration & signal to noise


Imagers vs. spectro-radiometers

Radiometer

TIMED-SEE, PROBA2-LYRA…– No spatial resolution– Spectral resolution!– Inflight re-calibrated– Full Sun

– More or less spectral resolution

– Avoid time gaps– Good cadence & SNR

EUV Imagers

SOHO-EIT, PROBA2-SWAP…– Imaging

Optical design or rastering

– Flatfield issues– Partial FOV– Multilayer passbands– Usually not 100% duty cycle

– Possible polarimetry– Photon limited


SWAP & LYRA« the High-cadence solar mission »

Image courtesy: Verhaert

• Launch end 2007 (2-year mission)• 60 cm x 70 cm x 85 cm, 120 kg• LEO dawn-dusk orbit• Demonstrate new space technologies

IIII


The solar payload of PROBA2

• LYRA– VUV, EUV & XUV radiometer– PI: JF Hochedez

– LYRA.oma.be

• SWAP– EUV imager– PIs: D Berghmans JM Defise

– SWAP.oma.beSun


LYRA highlights

4 channels covering a wide temperature range 1. 200-220 nm Herzberg continuum range2. Lyman-alpha (121.6 nm)3. Aluminium filter channel (17-70 nm) incl. He II at 30.4 nm4. Zirconium filter XUV channel (1-20 nm) (rejects strongly He II)

Traceable to radiometric standards– Calibration campaigns at PTB Bessy synchrotron

In-flight stability– Rad-hard, not-cooled, oxide-less diamond UV sensors– 2 different LEDs per detector– Redundancy (3 units)

High cadence (up to 100Hz) Quasi-continuous acquisition during mission lifetime


Dec 2005 tbc

April 2006 tbc


One of the 3 LYRA units


SWAP highlights

1 channel at 17.4 nm, 1kx1k CMOS-APS detector Detector and global instrument calibrated at PTB Good cadence

– 1 min consistent with spatial resolution

Quasi-continuous acquisition during mission lifetime– Duty cycle limited by telemetry only


PROBA2SWAP


SWAP TARGETS

Dimmings EIT wave Post-eruption arcade

Erupting prominences

Loop openings Plasmoid lifting

Flares

Spatial resolution:

Temporal resolution: - Nominal: - Optimal/max:

Spectral resolution:

How can SWAP and LYRA work together?

SWAP

3,11’’

1 mn～ 10s

17.5 nm1nm FWHM

LYRA

None

～ 50 ms 10 ms

[0,20]nm

[17,70]nm

121.6 nm

[200-220]nm

Time

… x 1200

Wavelength

0 mn 1 mn

Spectral information

Can we use the fact that the spectral overlap between the Al & Zr LYRA channels corresponds roughly to the SWAP pass band ?

– No TBC Can we use the 4 (wide ) LYRA pass bands to model 17.5nm?

– DEM-like, statistical and/or empirical methods 2 pass bands are optically thick

Wavelength (nm)

1 20

17 70

121

200 220


Plasma temperatures seen by SWAP and LYRA

Corona (cold 1MK, and ‘hot’ 10MK) Transition region + Corona. Corona mainly cold

LYRA & SWAP spectral coverage are very different

useful to think in term of T°

Contribution functions(assuming thermal equilibrium)

ZirconiumAluminium

SWAP

104 105 108106 107


Preliminary conclusions oncombining spectral information

Hard to “spectrally” combine LYRA and SWAP

But, LYRA Al and Zr include SWAP LYRA-Zr and SWAP observe ~same plasma


Using SWAP to identify the regions that make the irradiance vary

EUV irradiance model– track AR, QS, CH– Cf. NRLEUV (Warren et al

2001), Kretzschmar et al 2004

If success, whole spectral irradiance variability is modeled

– hence LYRA time series (at SWAP cadence only)

Mid-term variation


Using SWAP to identify the regions that make the LYRA irradiances vary

A prospectful new field

4 LYRA pass bands chronology of solar events in different parts of the solar atmosphere

Can we observe irradiance counterparts

– brightenings, dimmings, others?

SEM:0-50 nm

Small-term variations


Temporal evolution (1/3)Using radiometers to re-calibrate imagers

If roughly the same plasma, one expects similar normalized variations for integrated count rates

Cross-calibrations mutually improve long-term stability

SEM [0.5-50nm]

EIT 19.5 nm (integrated)

Comparing instruments with different aim(s) and pass bands…

e.g. SEM Flares not visible in the integrated EIT flux at 19.5

Temporal evolution (2/3)Contribution of solar regions to irradiance variations

Method:• Segment regions by hand on 1st image• Rotate images so that regions of interest appear always at the same position. • Not the best method but fast and quite easy• The rotation induces some unwanted effects

Results are indicative & illustrative

Data:1st of April 1997; Several flares and EIT wavesEIT image at 19.5 nm every 12 minIrradiance data from SEM

0.1-50 nm and 26-34nm, cadence 5 min

Temporal evolution (2/3)Contribution of solar regions to irradiance variations

last

First image

Last, and rotated

SEM [0.5-50nm]


Last image

Last image(rotated)

last

First image

Last, and rotated

SEM [0.5-50nm]


ACTIVE REGION 1 (AR1)

Last image(rotated)

last

First image

Last, and rotated

SEM [0.5-50nm]


ACTIVE REGION 2 (AR2)

Last image(rotated)

last

First image

Last, and rotated

SEM [0.5-50nm]


QUIET SUN 1 (QS1)

Last image(rotated)

last

First image

Last, and rotated

SEM [0.5-50nm]


QUIET SUN 2 (QS2)

Last image(rotated)

SEM 0.1-50 nm

SEM 30.4 nm

AR1

AR2

QS1

QS2 (around AR)

1. Most of the activity associated to AR1

2. AR2 anti-correlated?

3. Some SEM flares not seen in EIT

4. Finer details!

Instrumental pb

SEM 0.1-50 nm

SEM 30.4 nm

AR1

AR2

QS1

QS2 (around AR)

EIT difference images

SEM 0.1-50 nm

SEM 30.4 nm

AR 1

AR 2

QS 1

QS2

Bright front of EIT wave

Flare

.. And dimming


Temporal evolution (3/3)

Imagers can potentially compute irradiance for other heliospheric directions

– i.e. other planets– c.f. Auchère et al 2005

Use hi-cadence radiometer time series to decrease temporal aliasing in image sequences…

– Having assessed expected variability = f(x,y)


Using LYRA for aeronomy studies

PROBA2 has eclipse periods. During occultation, it will see the Sun thru the Earth’s atmosphere

This allows LYRA to measure the attenuation of the solar flux from which one can derive atmospheric properties

Apparent Sun diameter: 25 km

LYRA measurements


Using SWAP for aeronomy studies

Independent SWAP occultation observations

– Cadence limited – Only 17.4nm

– Imaging sequence No need to deconvolve for Sun area No need to assume disc homogeneity

SWAP measurements


Conclusion

Design new full Sun instruments meant to optimize the spectro-spatio-temporal balance!– Spectro-heliograph (such as on CORONAS-F)?– Array of >9 “low” spatial resolution multilayer

telescopes paving the accessible UV spectrum– Smart camera schemes autonomously

compromising between cadence and SNR



Quit complaining about your job!

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Synergies between solar UV radiometry and imaging