The Solar Chromosphere

Transcription

1 1 / 29 The Solar Chromosphere Recent Advances in Determining the Magnetic Fine Structure Andreas Lagg Max-Planck-Institut für Sonnensystemforschung Katlenburg-Lindau, Germany Rocks n Stars 2012

2 2 / 29 Table of Contents 1 The Chromosphere 2 Accessing the Chromospheric Field 3 The He I 1083 nm triplet 4 He I: Selected Highlights 5 Summary & Outlook

3 3 / 29 The Chromosphere In Hα

4 4 / 29 The Chromosphere In Hα

5 5 / 29 The Chromosphere In Hα

6 6 / 29 The Chromosphere In Hα

7 IBIS Fe I 5434 Å wing (K. Reardon) 7 / 29 The Chromosphere In Hα

8 IBIS Ca II 8542 Å wing (K. Reardon) 8 / 29 The Chromosphere In Hα

9 IBIS Ca II 8542 Å (K. Reardon) 9 / 29 The Chromosphere In Hα

10 IBIS Hα 6563 Å (K. Reardon) 10 / 29 The Chromosphere In Hα

11 The Chromosphere The Complexity Complex Chromosphere corona transition region hot plasma moss ~0.5 Mmclassical temperature minimum photosphere chromosphere ~1.5 Mm c s = c A ~1 Mm 0 Mm τ 500 = 1 convection zone spicule II C network Alfvén waves canopy domain D f i b r i l current sheets granulation E sub-canopy domain fluctosphere weak fields small-scale canopies / HIFs B reversed granulation p-modes / g-waves internetwork f i b r i l shock waves network A canopy domain F sub-canopy domain fluctosphere spicule I network dynamic fibril }supergranulation Wedemeyer-Böhm et al. (2008) 11 / 29

12 12 / 29 The Chromosphere The Complexity

13 The Chromosphere The Complexity Leenaarts et al. (2007) 13 / 29

14 The Chromosphere The Complexity Why is it so complex? Physical Conditions non-lte partial frequency redistribution (PRD) non-equilibrium hydrogen and helium ionization scattering 3D radiative processes Observational extremely short timescales low density plasma above bright background fine structure (fibrils) weak signals complex interpretation 14 / 29

15 The Chromosphere The Complexity Why is it so complex? Physical Conditions non-lte partial frequency redistribution (PRD) non-equilibrium hydrogen and helium ionization scattering 3D radiative processes Observational extremely short timescales low density plasma above bright background fine structure (fibrils) weak signals complex interpretation 14 / 29

16 The Chromosphere Key: Magnetic Field The Key is the Magnetic Field Rutten (2012) The principal ingredients defining chromospheric structure and dynamics are, for decreasing activity, magnetic reconnection, current heating, Alfvén waves, magnetically guided and/or converted acoustic waves, possibly gravity waves and torsional waves, and photon losses in strong lines. 15 / 29

17 Accessing the Chromospheric Field Extrapolations Accessing B Chromo : Extrapolations Method Use photospheric magnetic field vector (ideal: 3D vector field, 180 ambiguity resolved) Preprocessing: use e.g. Hα images to constrain magnetic field orientation consistent boundary data for nonlinear force-free modeling preprocessed boundary data are chromospheric-like expert: Thomas Wiegelmann (MPS) Problems errors in boundary conditions measurement errors ambiguity removal height of measurement model assumptions interesting regions not well-behaved / 29

18 Accessing the Chromospheric Field Extrapolations Accessing B Chromo : Extrapolations Method Use photospheric magnetic field vector (ideal: 3D vector field, 180 ambiguity resolved) Preprocessing: use e.g. Hα images to constrain magnetic field orientation consistent boundary data for nonlinear force-free modeling preprocessed boundary data are chromospheric-like expert: Thomas Wiegelmann (MPS) Problems errors in boundary conditions measurement errors ambiguity removal height of measurement model assumptions interesting regions not well-behaved / 29

19 Accessing the Chromospheric Field Extrapolations Extrapolations - Example Wiegelmann et al. (2005) 17 / 29

20 Accessing the Chromospheric Field Direct Measurements Accessing B Chromo : Measurements gyroresonant emission: Radio obs. of strong fields (>250 G) Bremsstrahlung emission: Radio coronal loop oscillations: EUV, coronagraphy Zeeman effect: spectropolarimetric observations UV - IR Faraday rotation: radio observation Scattering polarization: coronagraph Hanle effect: spectropolarimetric observations UV - IR 18 / 29

21 Accessing the Chromospheric Field Direct Measurements Accessing B Chromo : Measurements gyroresonant emission: Radio obs. of strong fields (>250 G) Bremsstrahlung emission: Radio coronal loop oscillations: EUV, coronagraphy Zeeman effect: spectropolarimetric observations UV - IR Faraday rotation: radio observation Scattering polarization: coronagraph Hanle effect: spectropolarimetric observations UV - IR 18 / 29

22 Accessing the Chromospheric Field Direct Measurements Accessing B Chromo : Measurements gyroresonant emission: Radio obs. of strong fields (>250 G) Bremsstrahlung emission: Radio coronal loop oscillations: EUV, coronagraphy Zeeman effect: spectropolarimetric observations UV - IR Faraday rotation: radio observation Scattering polarization: coronagraph Hanle effect: spectropolarimetric observations UV - IR Option 1 Full non-lte 3D treatment (Ca II H&K, Ca II IR) e.g. Oslo group (M. Carlsson, J. Leenaarts) 18 / 29

23 Accessing the Chromospheric Field Direct Measurements Accessing B Chromo : Measurements gyroresonant emission: Radio obs. of strong fields (>250 G) Bremsstrahlung emission: Radio coronal loop oscillations: EUV, coronagraphy Zeeman effect: spectropolarimetric observations UV - IR Faraday rotation: radio observation Scattering polarization: coronagraph Hanle effect: spectropolarimetric observations UV - IR Option 1 Full non-lte 3D treatment (Ca II H&K, Ca II IR) e.g. Oslo group (M. Carlsson, J. Leenaarts) Option 2 Hanle & Zeeman diagnostics using the He I nm triplet this talk 18 / 29

24 The He I 1083 nm triplet The He I 1083 nm triplet Centeno et al. (2008) 19 / 29

25 The He I 1083 nm triplet The He I 1083 nm triplet Centeno et al. (2008) 20 / 29

26 The He I 1083 nm triplet The He I 1083 nm triplet Centeno et al. (2008) Clue: For λ < 504 Å (= 24.6 ev) radiation originates in corona cannot penetrate deeply illuminates only upper chromosphere 20 / 29

27 The He I 1083 nm triplet The He I 1083 nm triplet Centeno et al. (2008) Pros and Cons simple: thin slab atmosphere Zeeman effect (+ simple Hanle) restricted height information weak signal in quiet Sun 20 / 29

28 The He I 1083 nm triplet The He I Sun of Avrett et al. (1994) 21 / 29

29 The He I 1083 nm triplet The He I Sun of Avrett et al. (1994) 21 / 29

30 He I: Selected Highlights Joshi et al. Sunspot Magnetic Field stay tuned for Joshi et al. (2012) 14:50-15:10 22 / 29

31 He I: Selected Highlights Xu et al. Active Region Filament Xu et al. (2012) Continuum image opposite polarities on both sides large penumbra-like structure roughly along the neutral line He I line core image Hα outlines complete filament He I only visible along few elongated field-aligned features 23 / 29

32 He I: Selected Highlights Xu et al. Active Region Filament - Inclination Xu et al. (2012) Opposite polarities in the chromosphere closer to each other than in the photosphere Chromosphere: small upflows along the PIL and inside the segmented He filaments. Downflows are found at its sides. 24 / 29

33 He I: Selected Highlights Xu et al. Active Region Filament - Azimuth Xu et al. (2012) nearly aligned along the PIL concave structure angle to PIL: Corona: the EUV loops even more perpendicular to the PIL 25 / 29

34 He I: Selected Highlights Xu et al. Active Region Filament - Scenario Xu et al. (2012) Characteristic signatures of a strong-field ( G) flux rope Flux rope produces filament during emergence 2 filaments overlying each other: 1 lower: concave topology 2 upper: normal configuration (unstable) Chromospheric field is not aligned with visual structure! 26 / 29

35 Summary & Outlook Larger Telescopes / Solar C Fine Structure & Short Timescales Ground Based GREGOR: 1.5 m on Tenerife NST: 1.6 m Big Bear ATST / EST: 4 m IBIS Ca II 8542 Å (K. Reardon) Space Borne Solar-C: 1.5 m, end of this decade 27 / 29

36 Summary & Outlook Larger Telescopes / Solar C Fine Structure & Short Timescales Ground Based GREGOR: 1.5 m on Tenerife NST: 1.6 m Big Bear ATST / EST: 4 m IBIS Ca II 8542 Å (K. Reardon) Space Borne Solar-C: 1.5 m, end of this decade 27 / 29

37 Summary & Outlook Larger Telescopes / Solar C Fine Structure & Short Timescales 27 / 29

38 Summary & Outlook Larger Telescopes / Solar C Fine Structure & Short Timescales Ground Based GREGOR: 1.5 m on Tenerife NST: 1.6 m Big Bear ATST / EST: 4 m IBIS Ca II 8542 Å (K. Reardon) Space Borne Solar-C: 1.5 m, end of this decade 27 / 29

39 Summary & Outlook Larger Telescopes / Solar C Fine Structure & Short Timescales Ground Based GREGOR: 1.5 m on Tenerife NST: 1.6 m Big Bear ATST / EST: 4 m IBIS Ca II 8542 Å (K. Reardon) Space Borne Solar-C: 1.5 m, end of this decade 27 / 29

40 Summary & Outlook Larger Telescopes / Solar C Summary & Outlook Conclusions Measuring chromospheric fields is high priority science goal Instrument developments: GRIS (GREGOR), FIRS, IBIS (NSO), Solar-C, Chinese Giant Solar Telescope (VIS-IR, 8 m) Model improvements: combined Hanle & Zeeman (MPS, IAC), 3D non-lte modelling of chromospheric lines (Oslo, soon: MPS) Missing link between photosphere and corona to be completed soon 28 / 29

41 Summary & Outlook Bilbiography Larger Telescopes / Solar C Avrett, E. H., Fontenla, J. M., & Loeser, R. 1994, in IAU Symp. 154: Infrared Solar Physics, ed. D. M. Rabin (Kluwer Academic Publishers, Dordrecht, 1994), Centeno, R., Trujillo Bueno, J., Uitenbroek, H., & Collados, M. 2008, ApJ, 677, 742 Joshi, J., Lagg, A., Hirzberger, J., & Solanki, S. K. 2012, in preparation Leenaarts, J., Carlsson, M., Hansteen, V., & Rutten, R. J. 2007, A&A, 473, 625 Rutten, R. J. 2012, Royal Society of London Philosophical Transactions Series A, 370, 3129 Wiegelmann, T., Inhester, B., Lagg, A., & Solanki, S. K. 2005, Sol. Phys., 228, 67 Xu, Z., Lagg, A., Solanki, S., & Liu, Y. 2012, ApJ, 749, / 29