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THE HELIOSEISMOLOGY PROGRAM OF PICARD

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. Heliosismology with PICARD. Why? Scientific objectives

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THE HELIOSEISMOLOGY PROGRAM OF PICARD

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  1. 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 Nice 03/12/2008

  2. Heliosismology with PICARD • Why? Scientific objectives • How? Helioseismic measurements with PICARD • Specifications (SODISM performances) Nice 03/12/2008

  3. Why? Scientific objectives • Structure and dynamic of the nuclear core(limb helioseismology and integrated irradiance data ) • The solar Dynamo, tachocline and torsional oscillations (Intensity Medium-l program or "Macro Pixels" program) • Fundamental (f) modes and the solar radius Nice 03/12/2008

  4. Scientific objective 1 : Structure and dynamics of the nuclear core • 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). • 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. Nice 03/12/2008

  5. Tracking Solar Gravity Modes Garcia et al, 2007: core rotation up to 3-5 times that of the radiative region ? Talks from T. Appourchaux, D. Salabert / R. Garcia, G. Grec Nice 03/12/2008

  6. 22 pixels PICARD How? g-modes search with PICARD: take advantage of limb-amplification • 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. Toner et al. 1999 Talk from J. Provost / T. Toutain Nice 03/12/2008

  7. 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 limb-amplification Nice 03/12/2008

  8. 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. Nice 03/12/2008

  9. The internal Rotation Inverse Problem Frequency, mHz angular degree, l Nice 03/12/2008

  10. Tachocline • 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 Corbard, 1998 Nice 03/12/2008

  11. 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

  12. 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

  13. 2. How? Helioseismic measurements with PICARD Helioseismology With Irradiance data: Talk of W. Finsterle Nice 03/12/2008

  14. 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

  15. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  16. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  17. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  18. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  19. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  20. 128x128 l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  21. 170x170 Nice 03/12/2008

  22. 256x256 Nice 03/12/2008

  23. 170x170 (no mask) l-nu diagram from 1-day MDI intensity Nice 03/12/2008

  24. 170x170 (Gaussian mask) Nice 03/12/2008

  25. Final Choice:256x256 (no mask) Nice 03/12/2008

  26. Relative differences between destructive and non destructive compression Nice 03/12/2008

  27. 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%). Nice 03/12/2008

  28. NOMINAL MODE Thanks to CNES Nice 03/12/2008

  29. 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. Nice 03/12/2008

  30. MODES CONSTRAINED BY THE EPHEMERIS • 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). Nice 03/12/2008

  31. 700-km scenario Limb: loss = 3.5 % MP : loss = 6.2 % Nice 03/12/2008

  32. operating modes: nominal, eclipses, calibrations (stellar, distorsion, …) Observational window Limbe Hélio : duty cycle = 93 % Nice 03/12/2008

  33. Macropixels : duty cycle = 78 % 50 mn aliases Nice 03/12/2008

  34. Macropixels : haute fréquence In principle OK, but be careful in case of large excursions of the signal (from the mean) Nice 03/12/2008

  35. 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

  36. 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 Nice 03/12/2008

  37. 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 possible No trouble for peak detection but, be careful in case of phase difference analysis and cross-correlation with contemporaneous data (SDO, SoHO). Nice 03/12/2008

  38. Photometry (Integration*gain) A tenth of solar noise σI/I ~ 9 ppm If only shutter noise: σt ~ 0.072 ms Nice 03/12/2008

  39. Integration time: simulations of a 50 ms (sigma) shutter noise sinewaves amplitude: from 1 to 10 ppm White noise level: 2.5 10-3 ppm2/mHz, OK ! If necessary, possibility of reducing this level by a factor 5 using the measure of the integration time Nice 03/12/2008

  40. Pointing Modeling  0.1 stability during the integration time (fine pointing by SODISM) • Digitization Modeling  14 digits are OK. Nice 03/12/2008

  41. 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 Nice 03/12/2008

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