The GREGOR Fabry-Pérot Interferometer Status, prospects, and scientific aims. Klaus G. Puschmann Leibniz-Institut für Astrophysik Potsdam (AIP)

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1 The GREGOR Fabry-Pérot Interferometer Status, prospects, and scientific aims Klaus G. Puschmann Leibniz-Institut für Astrophysik Potsdam (AIP) 1

2 Outline of the talk q Historical overview GFPI q Status GFPI (BLISS) Optical design Data acquisition system & Etalons Polarimetry (GFPI) Software Science verification (GFPI) Observational results (GFPI) q Research plan - GFPI (BLISS) Deciphering the nature of sunspots Overview: Umbral dots, light-bridges, penumbra Science goals with the GFPI Connection between photosphere and chromosphere How to confirm the actual picture of the chromosphere Advantage of BLISS and the GFPI and science goals q Summary & conclusion 2

3 Historical overview GFPI q Since early 90 s: Successful operation of the Göttingen Fabry-Pérot Interferometer at the German Vacuum Tower Telescope (VTT) q : First ideas concerning a spectrometer at GREGOR (Kneer & Hirzberger 2001, AN 322, 375; Kneer et al. 2003, AN 324, 302) q : First fundamental step towards the development of the GFPI. Integration of new etalons, cameras and sophisticated computer hardand software(puschmann et al. 2006, A&A 451, 1151). q Development of the GFPI optical design at GREGOR. Optical and opto-mechanical components purchased or manufactured (Puschmann et al. 2007, masfa.conf, 45) q Integration of a Stokes-vector polarimeter (Bello González & Kneer, 2008, A&A 480, 265) q 2009: Transfer of the GFPI to GREGOR (Denker et al. 2010, SPIE 7735, 6M) 3

4 Observations Date: 26 April 2006 NOAA AR10875 (θ=53 ) Observers: K.G. Puschmann, B. Sánchez Andrade Nuño FOV = 77 x 58 Image scale = / pixel Data Acquisition: GFPI VTT 126 spectral scans of the Hα line, Δ t = 17 s, t_exp=5ms 15 narrow-band (FWHM = 55 må) images per spectral 21 positions Δλ = må. DATA REDUCTION Reconstructed broad-band images Speckle reconstruction and narrow-band deconvolution (Puschmann & Sailer 2006, A&A, 454, 1011, Keller & v. d. Lühe 1992, A&A 261, 321) Correlation tracking 4

5 GFPI VTT Deconvolved line-core images Deconvolved line-wing images Sánchez-Andrade Nuño, B.; Puschmann, K. G., Kneer, F. 2007, msfa-conf, 70 Sánchez-Andrade Nuño, B. et al. 2008, A&A, 486, 577 5

6 GFPI VTT OBSERVATIONS Quiet Sun, disk center Date: 4 May 2006 Observers: K.G. Puschmann, I. Domínguez Cerdeña FOV = 77 x 53 (38 x 53 polarimetry, 29 x 43 after reconstruction), Image scale = /pix DATA REDUCTION Speckle reconstruction and narrow-band de-vonvolution (Puschmann & Sailer 2006, A&A 454, 1011, Keller & v. d. Lühe 1992) Correlation tracking and destretching Intensity, velocity and magnetic field maps Subsonic filtering Data Acquisition: 147 spectral scans of Fe nm with Δ t = 17 s, T_exp = 5 ms 15 narrow-band (FWHM = 26 må) images / spectral position, 20 positions, Δλ = 20.1 må. 6

7 GFPI VTT Network patch Intranetwork q Splitting and merging of magnetic field structures fingerprints in line core q Indication of flux annihilation, flux tube evacuation or upwards-propagating shock fronts Puschmann, K. G., Kneer, F., Domínguez Cerdeña, I. 2007, masfa.conf, 151 7

8 GREGOR FPI recent timeline q 2011: Comissioning of the GFPI Implementation of computer-controlled filter-sliders and preparation of the software for TCP/IP communication with external devices according to the Device Communication Protocol ->automated calibration and observations procedures (Puschmann et al. 2012, ASPC 463, 423) q 2012: Science verification of the instrument including a new blue imaging channel. Results concerning the performance of the instrument can be found in Puschmann et al. 2012, SPIE 8446, 79, (submitted to Optical Engineering) and Puschmann et al. 2012, AN 333, 880). q 2012 Design concerning optics, cameras, and etalons for the future integration of the BLue Imaging Solar Spectrometer (BLISS), a second Fabry-Pérot for the wavelength range nm (Puschmann et al. 2012, SPIE 8446, 79 (submitted to Optical Engineering)) Two molecular bands (G-band 430 nm and CN band-head 388 nm), All Balmerlines except H-alpha, and the Ca II H and K lines 8

9 Optical design GFPI ( nm) Table 3 M5 Up-to-scale drawing of the GFPI MP POL CCD1/F6 P2 M4 HL2 FPI2 NDF FPI1 CCD2/F6 WLS CCD1a/F5a IF1a CCD2a/F5a IF2a TL2a BS2a q Narrow-band channel (NBC) q Broad-band channel (BBC) q Blue imaging channel (BIC) Laser LL1 LFS LPF LL2 M3 HL1 FSL2 Table 4 Table 5 Table 1 TL4 TL3 CL1 FSCL P1a TL1a q Auxillary channels:, White-light channel Laser/photomultiplier channel. FCL Table 2 M2 FSL1 F5/FS2 BS2 TL2 P1 M1 CL2 TL1 BS1 FS1 F4 Optical elements of BIC labeled with a. Puschmann et al. 2012, SPIE 8446, 79 9

10 Optical design BLISS ( nm) Table 3 M5a MP P2 POL CCD1/F6 Laser LL1 LFS LPF LL2 M5 M4 HL2 FPI2 NDF FPI1 M3 HL1 M3a HL1a HL2a P2a LL2a FPI2a FPI1a NDFa LFSa LPFa POLa LL1a M4a CCD1a/F6a Laser_a FSL2a FSL1a MPa CCD2a/F6a TL4a TL3a F5a/FS2a TL2a CCD2/F6 FSL2 P1a Table 4 Table 5 Table 1 TL4 TL3 TL1a M2a BS2a Up-to scale drawing: Integration of BLISS into the GFPI q BLISS replaces the blue imaging channel of the GFPI. q Both Instruments have their NBC and BBC after the dichroic beam splitter BS1. q Optical elements of BLISS only defer in HL2a and TL4a F5/FS2 Table 2 FS1 M2 FSL1 BS2 TL2 P1 TL1 BS1 F4 Puschmann et al. 2012, SPIE 8446, 79 Optical Elements of BLISS denoted by a 10

11 Data acquisition systems GFPI nm BIC nm BLISS nm Camera 2x Imager QE 2x pco x pco.edge Detector Type CCD CCD CMOS Pixels Pixel Size [µm 2 ] Read out noise [e ] Full Well Capacity [e ] 18,000 60,000 30,000 Spectral Resp. [nm] QE 550 nm 380 nm 380 nm 530 nm 530 nm Digitization [bit] FOV 50 x x x 60 Image Scale / pixel / pixel / pixel Frame Rate [Hz] Blueshift [pm] 630 nm

12 Dual etalon system GFPI ( nm) BLISS ( nm) Manufacturer IC Optical Systems (ICOS) IC Optical Systems Diameter [mm] Finesse Reflectivity [%] Etalon Spacing [mm] FWHM [pm] 400nm FWHM Combined [pm] @400nm Resolution 250, ,000 Ghost Fraction [%] Controllers CS-100 (ICOS) CS-100 (ICOS) Spectral Scanning RS-232 RS-232 Coating

13 GFPI - Polarimetery Bello González & Kneer, 2008, A&A 480, 265) Polarimeter in front of NBC-camera: -> GFPI in dual beam vector spectropolarimetric mode q 2 ferro-electric liquid crystals (FLCs) and 2 polarizing beam splitters (calcites) for beamseparation (4.2 mm) q Half-wave plate exchanges ordinary and extra-ordinary beam -> astigmatism of same orientation in both beams-> removed by a toroidal lens q FLCs switched between 2 states -> full-stokes vector from 4 independent measurements Polarimetry with the GFPI: As soon the GPU (F2) is available for polarimetric calibration in the visible wavelength range 13

14 Control software Software package DaVis from LaVision q Adaptation to the spectrometer + GUI + scan tables: Puschmann et al q TCP/IP communication and automated observing and calibration procedures: Puschmann et al. 2012a,b Flow chart: Communications GFPI control computer (DaVis) - internal and peripheral devices. 14

15 Results: Science verification 2012 Counts and frame full spatial resolution: Filters: T=40%, FWHM=0.4nm, t exp =100ms -> 2000 counts -> 2 x 2 binning Filters with T=80% and FWHM= 0.7nm -> reasonable results without binning Spectral resolution and stray-light estimates: Estimate of PSF from pinholes images at different focal planes Energy enclosed in the PSF at the diffraction limit E(r DL ) -> estimate of the generic stray-light Radius r: 90% of the Energy enclosed -> estimate of spatial resolution Spatial sampling: confirmed for all 3 channels Stray-light: 10% after F4, 25% after F3, 40% after F2; all measurements without AO Spectral resolution: estimated from convolution of FTS with Gaussian of width σ + wavelength independent stray-light offset β (Allende Prieto et al. 2004, A&A 423, 1109). Problem: spectral resolution !!! FTS spectrum(red), FTS convolved with Airy function (orange), and FTS convolved with best-fit Gaussian kernel(blue). Blueshifts NBC & Spectral Sampling NBC: as expected 15

16 First observational results Observation: 31 July min time-series of AR NOAA S24 W18 (θ= 30 ) Fe I nm line, 86 steps, Δλ = 1.17 pm, t exp = 20 ms, Δt=64 s Data reduction: q Speckle reconstruction of BB Data (Puschmann & Sailer 2006) q Deconvolution of NB-data (Keller & v.d. Lühe 1994) q Blueshift correction of NB-data q Compensation for image rotation q Spatially alignment of data q Calculation of line parameters q Sub-sonic filtering, cutoff=5 km s -1 Image rotation of 5 in 22 min 16

17 First observational results Line scan across the Fe I nm line. Left panel: Deconvolved NB-images in spectral steps of 1.17 pm. Right panel: measured average profiles of QS (red), umbra (blue), and the FTS-profiles for comparison. Stars indicate the sampled spectral positions. 17

18 First observational results Active region NOAA Upper panels: speckle-reconstructed BB-image (620nm), speckle-deconvolved continuum (middle) and line core (right) NB-images. Bottom panels: line core velocity (left), ffhwm (middle), and EQW (right) 18

19 q q q q q q Work ahead for the GFPI Improvement of spectral resolution (Re-design Laser channel) New pentaprism for observation of Hα and higher wavelengths Performance at λ850 nm Polarimtery: Verification of the vector polarimetric mode Polarimetery: Implementation of an automated polarimetric calibration procedure Polarimeter: Extension of the usable wavelength range by addition of one variable FLCretarder (see Tomczyk et al. 2010) q q q q q Super-achromatic optical set-up ð exchange of the off-the-shelf achromats (TL1,TL2, HL1, & HL2 by Linos) by custom achromats At present chromatic focus shift away from wavelength in focus -> maximal wavelength distance 100 nm Integration of scmos cameras Larger FOV and 5x higher frame rates External white light source for all instruments (pupil around tip/tilt, DM) Automatic finesse adjustment (photodiode and AD-converter) q Polarimeter: Exchange of calcites: larger beam separation and FOV And now for something completely different -> Science with GFPI and BLISS 19

20 Research focus I Deciphering the nature of sunspots 45 min time series of MOMFBD reconstructed broadband images (602 nm) 1m Swedish Solar Tower. Sobotka & Puschmann (2009, A&A, 504, 575) ) 20

21 Umbral dots simulation & models Schüssler & Vögler (2006, ApJL 641, 73) Snapshot: magnto- convection umbra UD LB Penumbra Spruit & Scharmer (2006, A&A 447, 343) 21

22 Umbral dots - observations q Morpholigical studies of size, brightness, lifetime and horizontal velocities of UDs q Confirmation of UDs with dark lanes Sobotka & Puschmann 2009, A&A, 504,

23 Umbral dots & Light bridges - observations q Upflows related to dark lane of UDs with peripheral downflows up to 1 km/s and a size 0.25 q Better statistic concerning downflows missing q No finestructure in the coresponding magnetic field maps yet Ortiz et al. (2010, ApJ 713, 1282 ) Rouppe v. d. Voort et al. (2009, ApJL 718, 78) q q Upflows along central dark lane surrounded by weak down-flows similar to UDs Both results in agreement with magneto-convection in umbra 23

24 Light bridges magnetic properties q Decreased and more inclined B q Stronger and more vertical B at higher layers q Proposed scenario:field-free intrusion forces neighbouring B to bend over -> magnetic canopy SVST, LPSP Jurčák et al. 2006, A&A, 453,

25 Light bridges chromospheric activity CHROMOSPHERIC ACTIVITY ASSOCIATED WITH A SUNSPOT LIGHT BRIDGE q Ca brightness enhancements and strong photospheric downflows Louis et al. (2009, APJL 704, 29) Louis et al. (2008, Sol. Phys. 252, 43 ) Background: Ca image, Blue: strong downflows White: reduced field strenght Arrows: horizontal magnetic field 25

26 Science Goals - Magneto-Convection in Sunspot Umbrae with the GFPI q Improve morphological studies of umbral dots by spectropolarimetric observations at highest spatial and good spectral and temporal resolution. q Provide better statistics for the magnetic field reduction and flows adjacent to umbral dots at a spatial resolution down to about 50 km q Determine the physical mechanisms, which are responsible for the formation of umbral dots and lightbridges by means of spectral line inversions and geometrical modeling. q Identify processes leading to supersonic flows in sunspot light-bridges. q Evaluate the role of light-bridges in heating the lower chromosphere (in combination with BLISS, Ca II H) 26

27 Penumbra filamentary structure & Rimmele & Marino (2006, ApJ 646, 593) brightness q Uncombed penumbral model (Solanki & Montavon 1993, A&A, 275, 283): horizontal flux tubes embedded in more vertical background field harboring Evershed flow Improved e.g. Schlichenmaier (1998, 2003), Martínez Pillet (2000), Bellot Rubio (2004), Borrero (2010) q Gappy model (Spruit & Scharmer 2006, A&A 447, 343): bright filaments consequence of convective penetration of field free material. Sufficient energy to explain penumbral brightness. Uncombed model - difficulties in explaining brightness of 75%: No overturning convection, energy transported by Evershed flow? Problem: Ascending mass gets cooler at distances < length of a penumbral filament Ruiz Cobo & Bellot Rubio (2009, A&A, 488, 749): Analytical calculations of 2D heattransfer. Model assumes -> penumbral brightness of up to 50% of QS Puschmann et al. (2010, ApJ 720, 1417) : geometrical model: penumbral brightness explained by the energy flux of the ascending matter including deepest atmospheric layers 27

28 Penumbra - 3D MHD simulation MAGNETO-CONVECTION: Reproduces general properties of sunspots as compared with high resolution observations q Thermodynamic and magnetic field properties of penumbral fine structure q Outwards directed Evershed flow Rempel et al. (2009, Science 325, 171) Issues: q no mature penumbra q Dark cores (Scharmer 2002, Nature 420,151) form only occasionally q Long term stability and evolution of penumbra to be determined q To be confronted with observed properties of NCP 28

29 Penumbra Own work - Geometrical model Puschmann et al. 2010, A&A, 720, comp. SIR Inversion 5 nodes for T 3 nodes for B, v los 2 nodes for γ, ϕ Observation Full-Stokes Spectra of the AR taken with the Hinode/ SP on 1 May 2007 Selection: area with homogeneous radially aligned filaments. Area at θ=4.63 o (approx. disk center) v los identical to vertical velocity 29

30 Penumbra Geometrical heights z-coordinates for each pixel can be obtained by: unknown boundary condition for the integration : Wilson depression (Z W ) κ from P g and T ρ from equation of state retrieved from SIR assuming HE -> common geometrical height grid after integrating the above equation Abitrary Wilson depression for all pixels:. = 0 0 = Acceleration term Total Lorentz Gravitational Gradient of force force force gas pressure Minimization of a merit function by a genetic algorithm 30

31 Penumbra Stratifications of,γ, v z at 3 different geometrical heights. Temperature contrast strongly diminishes with height: 11% (z=0) to 3.7% (z=200) and change slightly no field free regions! changes from an upflow of 0.22 km/s (z=0) to ~0 (z=200) Contour lines enclose areas harboring significant Evershed flow v z > 0.3 km/s These areas are hotter smaller (but still ~ 1kG) more horizontal 31

32 Penumbra Net mass flow <ρv z > (g s -1 m -2) q Mean net mass flow (FOV) clearly positive q Mean ascending mass flow > 5 x mean descending mass flow q More pixels related to upflows q Overturning convection: cancellation of ascending and descending mass flow -> No clear signs of overturning convection in the FOV at 0.3 Energy flux (F E ) from ascending matter -75 to 0 km: (F E ) max > 5 F <F E > = 0.23F 0 to 100 km: (F E ) max F <F E > = 0.09F -225 to 200 km: <F E > = 0.78F!!!!! Energy transferred by ascending matter and energy employed in adiabatic expansion Specific heat Adiabatic gradient 32

33 Penumbra electrical current density Puschmann et al. (2010, ApJL, 721, 58 ) q J z (in color) and J hor (arrows:1 to 365 ma m 2 ) at z = 200 km. q Contour lines: Bz = 650 G (solid) and to 450 G (dashed) q J hor > 4 J z; q Significant J values at the border of intraspines Local Twist: Ruiz Cobo & Puschmann 2012, ApJ, 745, 141 q Components of B and J // central field line of the flux rope at each pixel in FOV q Similar result: Significant values at the borders of intraspines with opposite sign -> Background field wraps around intraspines Borrero et al 2008, A&AL 481, 13 33

34 Penumbra β= P g /P m q Wilson depression (z of τ=1 layer) at each pixel in the FOV q Red: elevated structures Blue: lowered areas q Arbitrary zero-scale for Z W no QS-calibration q White contours: v z > 0.3 km s -1 -> elevated areas q Map of plasma β at z = 0 km. q Contour lines: Bz=650 G (solid), 450 G (dashed) q β=1 surface strongly corrugated q Intraspines: beta > 1 Spines: one order of magnitude lower 34

35 Science Goals - Structure and Kinematics of Sunspot Penumbrae (GFPI) q Examine the relationship between penumbral fine structure, Evershed flow, and magnetic field at spatial scales down to about 50 km q Investigation of possible associations between up-flows and down-flows with photometric and magnetic properties of penumbral filaments to confirm or reject magneto-convection q Determine the three-dimensional structure of the entire sunspot as a function of geometrical height and constrain numerical sunspot models. q Discrimination between competing penumbral models. 35

36 Research focus II: Connection between Photosphere and Chromosphere Structure QS l T 1 > T 0 l l l l Magnetic fields expand in the chromosphere, horizontal canopy Turbulent / horizontal magnetic fields Acoustic waves MHD-waves inside fields How can this picture be confirmed??? 36

37 2D Lyot filter imaging in QS Time series of Ca II K Lyot imaging q 2D spatial resolution, temporal resolution q no spectral resolution, no height information! 37

38 Time series of slit-spectra in Ca II H + LTE inversion Beck, Rezaei, Puschmann 2012, A&A, in press; ArXiv D spatial resolution, temporal resolution, high spectral resolution, high height resolution But: the second spatial dimension is missing! 38

39 Individual wave events in time series of slit-spectra l Temperature at one pixel with time and height Chromospheric bright grains: caused by wave propagation from the photosphere to the chromosphere (Carlsson & Stein 1997, ApJ 481, 500) l Energy density of 45 J/m 3 total energy of 2 * J Beck, Rezaei, Puschmann 2012, A&A, submitted 39

40 Large-area scan of slit-spectra in Ca II H + LTE inversion Beck, Rezaei, Puschmann 2012, A&A, submitted 2D spatial resolution, spectral resolution... but: no temporal resolution! 40

41 Individual features in 2D map 3D temperature cubes -> topology of thermal structures q Flux tube at center: connection to photosphere, expansion with height But: no temporal resolution! q Shock wave at the center, no connection to photosphere 41

42 Chromospheric temperature rise: difference AR - QS Relative occurrence of temperatures in QS and AR in the LTE inversion; dashed: average T thick black line : original HSRA model. Beck, Rezaei, Puschmann 2012, A&A, submitted Average temperature in AR exhibits temperature rise 42

43 Science goals - Connection between Photosphere and Chromosphere q BLISS: 2D spectroscopy at medium to high temporal resolution and moderate spectral resolution at spatial scales down to 40 km. q Combination with Ca II IR spectra and photospheric magnetic information obtained with the GFPI q Quantitative estimate of contribution magnetic -- nonmagnetic heating processes. q Distinguish the wave modes present in the solar atmosphere (acoustic, magneto-acoustic, gravity waves). q Direct comparison with models and simulations q Improvement of analysis methods including NLTE-inversion. NICOLE? 43

44 Summary & conclusion q GFPI & BLISS: Dual etalon spectro(polari)meters for the wavelength range nm and nm. q Combination: fast narrow-band imaging - Adaptive Optics - image reconstruction techniques (Puschmann & Beck 2011, A&A, 533, 21) -> potential for discovery science concerning the dynamic Sun and its magnetic field down to spatial scales of about 50 km and 40 km, respectively q High spatial resolution in a 2D FOV q Medium to high temporal resolution (1-2 min) q Medium to high spectral resolution (250,000; 100,000) q Combination of suited inversion codes and a post-facto conversion to geometrical heights -> 3D T,V,B-cubes with additional temporal resolution -> Determination of all thermodynamic and magnetic properties -> exact and quantitative study of all relevant physical processes and a direct comparison with competing models and simulations 44