Measurements of Solar Magnetic Field in Huairou Solar Observing Station (HSOS)

Transcription

1 Measurements of Solar Magnetic Field in Huairou Solar Observing Station (HSOS) DENG Yuanyong Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences

2 Solar Observations in China

3 Ming antu Solar Radio Station for Chinese Spectral Radioheliograph CSRH Coming soon Huairou Solar Observing Station Beijing Inner Mongolia 2011 Sept 2011

4 Nanjing University 60cm Solar Tower H monitor Nanjing Institute of Astronomical optical Technology Beijing Purple Mountain Observatory Nanjing ONSET Solar spectrum in visible and near infrared Fine structure of solar photoshere and chromosphere

5 Full-disk H Monitor 1m Solar Tower Beijing Yunnan Astronomical Observatory Nanjing Kunming

6 Beijing In the future somewhere here Next generation of big solar telescope Nanjing Kunming

7 首页目录 Solar Radio Spectrometers At Huairou, NAOC: Frequency range Spectral res. Time res. Sensit ivity Dyna. range Pol. Work ing GHz 20 MHz 50 ms 2% So 10 db Yes GHz 10 MHz 8 ms 2% So 10 db Yes GHz 20 MHz 5 ms 2% So 10 db Yes 1999 At Purple Mountain Obs.: GHz 10 MHz 5 ms 2% So 10 db No 1999 At Yunnan Astronomical Obs. : GHz < 3 MHz 5 ms 2% So 10 db Yes 2000

8 HSOS IS the only one who carries out observations of solar magnetic field in China (filter-type magnetograph)

9 Huairou Solar Observing Station (HSOS) Since 1999 Since 1984 Since 2005

10 Solar Magnetic Field Telescope (SMFT) Huairou vector B + Trace images (Zhang H. et al., 2003, )

11 35cm Solar Magnetic Field Telescope (since 1984) Vector magnetogram and Dopplergram tunable birefringent filter FeI 5324, H 4861, FWHM=0.15Å, photosphere FWHM=0.24Å, chromosphere FOV: 6 *4 (max., depends on CCD) Sensitivity: 10G (longitudinal) 200G (transverse) deep integration available (~a few Gauss) Spatial Res.: 1---several arcsec. Temporal Res.: <1min. Cadence: hour Daily observations

12 Full Disk Vector Magnetograph at Huairou since 2005 VMG Aperture 10cm Line FeI Å 1K*1K (2K*2K being developed) Full-disk H_alpha Aperture 20cm CCD 2K*2K

13

14 60cm Three-Channel Solar telescope since 2009 Vector magnetogram tunable multi-channel birefringent filter FeI 5250/5247, MgI5173, simultaneously FWHM~0.05Å for FeI, and 0.1 for MgI FOV: ~3 *3 Daily observations since

15 Observation of Vector Magnetic Field

16 Physical quantities that can be derived Shear angle Current (J z ) Twist ( z ) Twist ( best ) Current helicity (h c ) Free energy B s B f B o E free B s 8 2 All these quantities indicate the non-potentiality of the measured field.

17 Scientific questions that could be targeted Vector magnetic field on the photosphere Extrapolation of coronal magnetic field Measure non-potentiality: - Shear angle - Current (J z ) - Twist ( z ) - Twist ( best ) - Current helicity (h c ) - Free energy Variation associated with flares and CMEs Flux emergence process Helicity produced by solar dynamo

18 Bastille Day events

19 Shear Angle s angle( Bp, Bo ) 01:35 B o : Observed field B p : Potential field ~8.5 hr Scaler: 60 Contour: 80G 10:24 Flare

20 Vertical Current j z B ( x y B x y ) 01:35 B x, y Observed transverse field ~8.5 hrs Scaler: 0.02A/m 2 Contour: 80G 10:24 Flare

21 Current Helicity 01:35 h z j z B z ~8.5 hrs Scaler: 0.075G 2 /m Contour: 80G 10:24 Flare

22 Source Field B B s B Free Energy E f free f ---LFFF B B s 8 2 o 01:35 ~8.5 hrs Scaler: erg/cm 3 Contour: 80G : 0.013, 0.004, 0.013, , 0.004, , 0.002, :24 Flare

23 East---West Deep integration mode and weak magnetic field South-North Mosaic image

24 Several years earlier than Hinode Vector Magnetogram in Solar Polar region

25 Chromospheric observation with H 4861Å Photospheric magnetogram Chromospheric magnetogram Chromospheric Dopplergram H flare

26 Chromospheric magnetogram of a unipolar region at wavelength 0.40 to -0.12Å from the H line center (Zhang et al, 1991)

27 Photoshpere Similarities Between Quiet-Sun Magnetograms Chromoshpere (Zhang M. et al 2000).

28 Statistics research of vector magnetic field based on HSOS 25yrs obs 84% negative 81% positive distribution of the sign of current helicity in the two hemispheres during the cycle 22 with 442 ARs (Bao & Zhang1998).

29 Derived field lines show consistence with H α image. (Wang HN et al., 2001) H.N., Wang et al., 1999 Using Huairou vector magnetogram and a reconstruction method proposed by Yan & Sakurai (1997)

30 2005 全球华人空间 / 太空天气学大会 Global magnetic connectivity in Bastille-day events of 2000

31 Global magnetic connectivity in Bastille-day events of 2000 Wang J., et al, 2004, 2005 Wang J., et al, 2004, 2005

32 Observation of Magnetic Field: Limitations of current used methods Fundamental structure of magnetic filed Spectral information vs imaging Model-dependence inversion Sensitivity of traverse components and Multi-layers vector magnetogram

33 Spatial resolution

34 what is the end of fine feature of the sun? RESOLUTION: 6 km = arcsec INTENSITY VERTICAL Veocity

35 Already have many diffraction-limited observations in the world (SST, NVST, NST ) However, they are only images (white-light or filtergram), not magnetograms! For magnetic field, not only spatial resolution, but also magnetic sensitivity, are necessary (Deng et al, 2009) Hopeful in the future ATST, CGST

36 Spectral Observation vs Imaging Observation two traditional solar observations Solar spectrum of line source Optical system spectrogr aph slit Monochromatic image of Two-dimensional source Optical system + narrow-band birefringent filter Irkutsk

37 Spectral Observations: spectrograph Spectrum Higher accuracy of magnetic measurement temperature, velocity, density, etc.. Line source along slit, (not image!) have Seen the trees, haven t seen the forest!

38 Imaging observations: Birefringent filter, FP Two-dimensional objective (image) Follow the evolution of solar magnetic field and the dynamic process of solar activity Monitor and forecast the solar eruptive events No spectrum, and thus less physics informations Relatively lower accuracy have known it, haven t known why it is

39 How can see both the trees and the forest? Spectrograph: spatial scan perpendicular to the slit Filter: change the passand, spectral scan two-dimensional spectrograph However: Solar-B/SP,imaging time ~90min Filter, tens of minute to get spectral profile SDO/HMI, limited spectral point and not simultaneous

40 Two-Dimensional Real-Time Spectrograph---2DS Principally, it is a Lyot filter, under developping Traditional Lyot Filter Multi-channel Lyot Filter PBS---polarizing beam splitter

41 8 passbands for an 8-channel birefringent filter

42 Multi-passband in one solar spectral line Absorption line Passband of birefrigen filters Each passband is an individual Lyot filter; 8 passbands can construct a rough Stokes profile at same time However, still limited spectral samples!

43 Fiber Arrayed Solar Optical Telescope (FASOT) (Qu et al., YNAO) prototype under test

44 Raw data 5*5 array Reconstructed image

45 Reconstrctued Stokes V Challenges in technology : large array, less size of fiber (spatial resolution), uniformity

46 Inversion of Stokes parameters Radiative transfer equations for Stokes parameters

47 ,, B T, S are extremely model dependent, even themselves need to be determined For example, in SDO/HMI inversion code, you may have more than 20 unknown numbers to be derived, but you only have six spectral samples Hinode/SP is much better, but you still need models and assumptions too

48 Zeeman effect = gb 2 whereas, the width of spectral line is proportional to Thus, direct measurement of Zeeman split in infrared spectrum? model-independent ATST, EST, CGST

49 Problem for the traverse components J. Evans in 1960s, for the magnetograph based on Zeeman effect: B t 70B V 1/2 Bt is the magnetic sensitivity of traverse component, Bv for longitudinal Thus, up to now, we don t have accurate vector magnetic measurement in order of a fews tens Gauss So, what is the reliability in quantitative study, for example, helicity?

50 For the same reason, it is difficult to get vector magnetic information in upper atmosphere, for example, chromosphere Thus, only the Jz and Hcz can be derived from observables,cannot for Jx,y and Hcx,y How about the direct measurement of Zeeman split in infrared spectrum? Maybe ok!

51 Chinese Giant Solar Telescope ---CGST Proposed by: National Astronomical Observatoreies, CAS (NAOC) Yunnan Astronomical Observatory, CAS (YNAO) Purple Mountain Observatory, CAS (PMO) Nanjing University (NJU) Nanjing Institue of Astronomical Optical Technology, CAS (NIAOT) Beijing Normal University (BNU)

52 CGST overall Ring Solar Telescope Diameter: 8m (spatial res. 0. Effective area: 22 m 2 (5m full-aperture telescope) Spectral converge: 0.4 to 15 m FOV: ~3 Scientific Instruments Two-dimensional real-time spectrograph (2DS) Fibre Arrayed Solar Optical Telescope (FASOT) F-P etolan AO/MCAO Highest spatial resolution and magnetic sensitivity Infrared and optical Solar telescope

53 Jan. 2010, selected and recommended by CAS to National Development and Reform Commission (NDRC, 发改委 ) as National major basic scientific project for Nov., 2010, selected by NDRC as a national 14-5 th ( ) planning project for astronomy Feb. 2010, selected by Chinese NSF as 13-5 th ( ) planning project for astronomy Aug. 2010, site survey and FASOT were Supported by NSFC (1.86M and 1.84M RMB) Oct. 2010, pre-research of CGST key science and technology supported by CAS (2.6M RMB) Aug. 2011, proposal of key method and technology for mid-infrared solar polarization measurement was Supported by NSFC (1.8M)

54 Budget (estimated in 2009): ~600M RMB 10 15years Site: western part of China (Tibet ) International collaboration is eagerly expected!

55 Thanks!