Nice 03/12/2008

THE HELIOSEISMOLOGY

PROGRAM OF PICARD

T. Corbard, O.C.A.

T. Appourchaux, I.A.S.

P. Boumier, I.A.S.

B. Gelly, THEMIS

R.A. Garcia, S.J. Jiménez-Reyes, J. Provost, T. Toutain, S. Turck-Chièze, et al

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1. Why? Scientific objectives

2. How? Helioseismic measurements with PICARD

3. Specifications (SODISM performances)

Heliosismology with PICARD

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Why? Scientific objectives

1. Structure and dynamic of the nuclear core(limb helioseismology and integrated irradiance data )

2. The solar Dynamo, tachocline and torsional oscillations (Intensity Medium-l program or "Macro Pixels" program)

3. Fundamental (f) modes and the solar radius

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Scientific objective 1 : Structure and dynamics of the nuclear core

The main interest of this part of the spectra is that these modes are more sensitive to the deepest layers that remain poorly known both in terms of their structure and their dynamic.

The knowledge of the solar core properties is crucial to understand the dynamical evolution of the Sun and Stars and to set new constraints on neutrino physics.

All the measurements that will be obtained by PICARD for helioseismology are for improving our knowledge of the low frequency domain of the solar oscillation spectra (low and intermediate degree modes).

Nice 03/12/2008

Garcia et al, 2007: core rotation up to 3-5 times that of the radiative region ?

Tracking Solar Gravity Modes

Talks from T. Appourchaux, D. Salabert / R. Garcia, G. Grec

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How? g-modes search with PICARD: take advantage of limb-amplification

Toner et al. 1999

• This limb amplification is understood theoretically (Toutain et al. (1999)) and it has been observed for p-modes using MDI images and LOI guiding pixels.(Appourchaux et al. 96)

• PICARD will have a resolution and a stability allowing us to use this amplification factor for searching low frequency modes.

22 pixels PICARD

Talk from J. Provost / T. Toutain

Nice 03/12/2008

limb-amplification

Toner, Jefferies & Toutain 1999

Seismic Radius and f-modes: Talks from H.M Antia and S. Lefebvre

Leaks problem: Talk from M.C. Rabello-Soares

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Scientific objective 2 : Solar dynamo, tachocline and torsional oscillations

One of the major challenges in solar physics is to understand the origin of the magnetic activity cycle of the Sun.

Helioseismology does not give direct access to the internal magnetic field strength but it is a very powerful tool to infer the internal rotation rate, and some useful information on the magnetic field can also be deduced from its predicted interaction with the observed velocity field.

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The internal Rotation Inverse Problem

angular degree, l

Fre

quen

cy,

mH

z

drdθθ)Ω(r,θ)(r,Km

ωωnlm

nlmm-nl

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Tachocline

Corbard, 1998

The tachocline is a thin shear layer at the interface between the convection zone and the radiative interior, in which it is likely that a strong magnetic field is built as a result of the dynamo Ω-effect

From the study of the tachocline properties (structure, extent, precise location and latitudinal shape) we can derive not only the precise profile of the rotational shear but also get some hints on the shape and strength of the magnetic field at this depth

The tachocline is sensed mostly by p modes with degrees 20 < l < 60 but higher modes are also needed for inversion.

Tachocline

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Torsional Oscillations in the convection zone

When compared to the time averaged profile, angular velocity shows bands of enhanced rotation rate that migrate toward the equator during the increasing phase of activity

It is very likely that we have here a direct observation of the back reaction of the dynamo magnetic field on the rotational profile, from which the toroidal field originates within the tachocline

Allows us to constrain our models of the interplay between magnetic field and convection

Nice 03/12/2008

Scientific objective 2 : Solar dynamo, tachocline and torsional oscillations

Detecting modes up to l=250 and measuring frequencies and splittings should allow us to probe the tachocline and most of the convection zone.

All these objectives are also major objectives for SDO.

In this field SDO is expected to provide much better data with more resolution, better signal to noise ratio (in velocity)…

It is however interesting to have both Intensity and velocity signals and to have measurements from two different instruments

Talk of T. Straus

Nice 03/12/2008

2. How? Helioseismic measurements with PICARD

InstrumentData Filter

[band]Cadence Exposure time

SODISM 22" wide rings of 1" pixels across the limb.

535.7 nm [0.5]

2 mn 8 s

SODISM 256x256 Images of 8" macro- pixels

535.7 nm[0.5]

1 mn 8 s

PREMOS SpectralIrradiance

215 nm[7]

0.1s 0.1s

PREMOS SpectralIrradiance

268 nm[7]

10s 10s

PREMOS SpectralIrradiance

535.7 nm[0.5]

10s 10s

PREMOS SpectralIrradiance

607.2 nm[0.8]

10s 10s

PREMOS SpectralIrradiance

782.3 nm[1.7]

10s 10s

SOVAP BolometricMeasurements

NA 10s 10s

SOVAP Total Irradiance

NA 3 mn 10s

PREMOS TotalIrradiance

NA 2 mn 20s

HelioseismologyWith Irradiance data: Talk of W. Finsterle

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Intensity Medium ℓ program of PICARD

Images 256x256 (8"x8" Macro Pixels) with non destructive compression and no Gaussian mask. 1mn Cadence. 77% DC expected. (very demanding for available TM. Higher resolution was favored against the possibility of Gaussian masking )

The pipeline is under development in collaboration with Sebastian Jimenez-Reyes based on the pipeline he developed for LOWL.

Tests are being performed using MDI intensity images corrected for limb distortion and provided by Cliff Toner

Heliosismology Quick look Software for the mission center have been devilered (Beta versions).

Talk of D. Salabert

Talk of C. Renaud

Nice 03/12/2008

l-nu diagram from 1-day MDI intensity

128x128

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l-nu diagram from 1-day MDI intensity

128x128

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l-nu diagram from 1-day MDI intensity

128x128

Nice 03/12/2008

l-nu diagram from 1-day MDI intensity

128x128

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l-nu diagram from 1-day MDI intensity

128x128

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l-nu diagram from 1-day MDI intensity

128x128

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170x170

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256x256

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l-nu diagram from 1-day MDI intensity

170x170 (no mask)

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170x170 (Gaussian mask)

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Final Choice: 256x256 (no mask)

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Relative differences between destructive and non destructive compression

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OPERATIONAL MODE

Nominal:

no satellite manoeuvres, no calibration phase, no physical events.

Limb: 1 image every 2 minutes; MP: 1 image per minute.

But:

MP: LCO (4%), diameter (10%), FFL + FCO (0.14%), loss (0.27%)

duty cycle (MP) ~ 85.5%.

(Limb loss estimated < 0.8%).

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NOMINAL MODE

Thanks to CNES

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CALIBRATION MODES

Optical distorsion:

- optics and CCD calibration; a 30 arsec-step roll of the satellite, once a month.

- duration: 937 minutes (JPM; 22/10/2007) loss of 2.2% of duty cycle

Stellar:

- angular/pixel relationship calibration; pointing toward the barycenter of 2 stars, 4 times per year.

- 94 minutes per operation: 0.07% loss.

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Absorption:

- line of sight crosses the Earth atmosphere at an altitude lower than 40 km; a several-day period twice a year (just before and after the night mode).

- 9 minutes at maximum, for each orbit, during which a single wavelength wide limb will be measured.

10 days 0.2%.

Night:

- eclipses (Sun hidden by Earth); 3 months once a year.

- 2 phases in the perturbation: night itself (maximum of 18 minutes per orbit for a 700-km altitude), and a thermal reequilibrium after the satellite left the shadow (14 minutes at maximum).

MODES CONSTRAINED BY THE EPHEMERIS

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700-km scenario

Limb: loss = 3.5 %MP : loss = 6.2 %

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Observational window

operating modes: nominal, eclipses, calibrations (stellar, distorsion, …)

Limbe Hélio : duty cycle = 93 %

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Macropixels : duty cycle = 78 %

50 mn aliases

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Macropixels : haute fréquence

In principle OK, but be careful in case of large excursions of the signal (from the mean)

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Specifications – instrumental noise

Sampling

3 years 10 nHz resolution

for a 100 μHz peak (limb): 100 ppm for a 3 mHz peak (MP): 3 ppm

maximum drift over the whole mission: ~ ppm

drift compensation of the on-board clock: once a week: < 80 ms

Nice 03/12/2008

simulations with systems input; a 1 ms jitter on the 1-minute sampling

+ 20 ms/week trend + systematic errors + margins.

Redistribution of the spectral energy of sinewaves < 10-3

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Specifications – instrumental noise

Sampling

3 years 10 nHz resolution

for a 100 μHz peak (limb): 100 ppm for a 3 mHz peak (MP): 3 ppm

maximum drift over the whole mission: ~ ppm

drift compensation of the on-board clock: once a week: 80 ms at maximum

Note: reference time is TUC, not TAI leap second possibleNo trouble for peak detection but, be careful in case of phase difference analysis and cross-correlation with contemporaneous data (SDO, SoHO).

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Photometry (Integration*gain)

A tenth of solar noise σI/I ~ 9 ppm

If only shutter noise: σt ~ 0.072 ms

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Integration time: simulations of a 50 s (sigma) shutter noise

White noise level: 2.5 10-3 ppm2/Hz, OK !If necessary, possibility of reducing this level by a factor 5 using the measure of the integration time

sinewaves amplitude: from 1 to 10 ppm

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Pointing

Modeling 0.1 stability during the integration time (fine pointing by SODISM)

Digitization

Modeling 14 digits are OK.

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Conclusion

Performances seem OK; many thanks to the project team (CNES + labs).

Algorithms strategy (gap filling for MP ?)

Modelling for scientific interpretation + inversion

Coordination of the collaboration with SDO

Working groups in charge of:- In flight performances validation- validation of each level of data

CO-I and G-I proposition to the CS