1 / 28

On Flux Spectra of Solar Intranetwork Magnetic Elements Jingxiu Wang, Guiping Zhou, Hui Li et al.

On Flux Spectra of Solar Intranetwork Magnetic Elements Jingxiu Wang, Guiping Zhou, Hui Li et al. I. Introduction.

marja
Télécharger la présentation

On Flux Spectra of Solar Intranetwork Magnetic Elements Jingxiu Wang, Guiping Zhou, Hui Li et al.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. On Flux Spectra of Solar Intranetwork Magnetic ElementsJingxiu Wang, Guiping Zhou, Hui Li et al.

  2. I. Introduction • Solar Intranetwork (inner-network, inter-network) fields (IN) were first described by Smithson (1975), Livingston & Harvay (1975) as `discrete elements' of mixed polarities `interior to network'. • A few key papers (Keller et al. 1994; Wang et al.1995; Lin 1995) in the middle of 1990s largely renewed the interests in IN field studies. • A new era of relevant studies is opening by Hinode observations

  3. Are IN fields intrinsically weak or strong? • What is the contribution of this weak field component to the Sun's magnetism and atmosphere heating? • How do they correlate with convection and plasma flow • What is their role in heating of solar atmosphere? • How do they Influence the opening coronal structure? • What is their origin? • How do they act in solar cycle? There is a magnetic dichotomy on the Sun (Wang et al. 1995; Schrijver & Zwaan, 2000))

  4. Some of the best ground-based observations Roughly the same size of FOV, 31X31 Very high resolution High sensitivity Lites, 2002, ApJ 573,431 (ASP Sac Peak) Bergers et al. 2004 A&A 428, 613 (SST) Wang et al. 1995 Solar Phys. 160, 227 (Big Bear)

  5. Understanding the horizontal fields

  6. Perspectives of current work • Intrinsic fields strength • Apparent flux density • Flux distributions • Locations & area occupied • Difference between infrared and visible measurements • Internal Structures • Polarity distribution • Horizontal IN

  7. Perspectives of current work • Evolution • Velocity patterns • Lifetime • Rate of flux emergence and disappearance • Non-potentiality & topology • Atmospheric response • Relative contributions to the Sun’s magnetism • Classification • Origin • Solar cyclic changes

  8. Flux distributions • Wang et al.(1985) – smallest observable flux 1016 Mx • Shi et al. (1990) – 21016-1018 Mx; • Wang et al. (1995) – magnetic dichotomy; IN with peak distribution at 61016Mx & NT at 21018 Mx; Power law after the peak distribution • Lin (1999) – majority of magnetic features < 51016 Mx • Meunier et al.(1998) – lognormal distribution similar to sunspot of Bogden et al. (1988) • Parnell (2002) – Weibull PDF • Khomenko et al.(2003) – TIP FeI 15648 noise (2-3) 10-4 smallest 21015 Mx • Sanchez Almeida et al.(2003) – only 10% flux could be detected by current magnetograms, IN far more flux in ARs • Hartj & kneer (2002) – Gregory Coude Tel. Stokes V 6302 (1-5)1016 Mx appears different from Gaussian distribution (power law?) • Lites & Socas-Navarro (2004) – no significant increase in unsigned flux when resolution was improves to 0.6 • Dominguez Cerdena et al.(2006) – PDF combined Hanle & Zeeman measurements: significant fraction of unsigned flux (75-90%) contributed by fields < 500G

  9. Rate of IN flux emergence • Zirin (1985) – earlier suggestion: 2 order of magnitude faster than AR, one order faster than Ephemeral Region (E.R.) • Wang et al. (1995) – Fully confirm Zirin’s estimation; Now,intranetwork E.R. were seen within each network (also Hinode) and at granulations The IN elements seen to contribute the most of the Sun’s magnetic flux

  10. II. Tentative work with Hinodeon flux spectra of IN elements • Understanding the calibrations • Flux distribution and intrinsic field strength • Appearance and disappearance • Lifetime • Understanding horizontal magnetic fields • Overall relationship of IN fields, intensity, and convection

  11. Enhanced netwok (S04W02)20:51, 22:24, on 11 Dec. 2006 (0.16”, △T=2min, 701x908 pixel2; TF Fe I 6302)

  12. Quiet Sun (N03W05)17:35, 20:48 on 24 June 2007 (0.16”, △T=1min, 914x995 pixel2; TF Na I 5896)

  13. Calibration: 9000*V/I= 1 MDI Gauss in enhanced • SOHO/MDI: Fe I Pixel area: 0.370 arcsec2 • Hinode/SOT: Fe I 6302 A • Pixel area: 0.026 arcsec2

  14. Calibration: 8000*V/I= 1 MDI Gauss in quiet sun • Hinode/SOT: Na-D • Pixel area: 0.026 arcsec2 • SOHO/MDI: Fe I • Pixel area: 0.370 arcsec2

  15. Calibration: 1.2x105*V/I= 1 SP G in NET elements • SOT/FGIV: Fe I 6302 A • Pixel area: 0.026 arcsec2 • SOT/SP: Fe I 6302 A • Integration: 20:00-21:03

  16. Calibration: 1.1x105*V/I= 1 SP G in IN elements • SOT/FGIV: Fe I 6302 A • Pixel area: 0.026 arcsec2 • SOT/SP: Fe I 6302 A • Integration: 20:00-21:03 Assuming a filling factor about 0.08 then the SP and FG provide the same apprant flux density

  17. Flux distributions seen in FGIV data (More than 10,000 IN elements were identified and flux measured)

  18. Flux distribution function fitted by Weibull function Here,  is scale parameter;  is shapeparameter; 0 is locationparameter. For the intra-netwrok elements,  is close to 2.3×1016 Mx,  can be taken as 1.13, 0 is 0.7×1016 Mx. The PDF is positively skewed with right tails. But what physics determines the scale and location parameters?

  19. Flux appeared in clusters of mixed polarity; Many of them may, in fact, consist of ephemeral regions (ERs) in further high resolution

  20. Flux emergence in the form of tiny ephemeral regions (ERs)

  21. An opposite polarity pair approach and cancel first, then grow and separate

  22. Disappearance of IN elements cancellation fading In-situ fragmentation coalescence

  23. Overall Statistics of IN flux • Fractions of IN flux are 0.10-0.19 and 0.17-0.34 of Sun’s magnetic flux at any given time for enhanced and quiet network areas (allowing a half of NT flux were missing in our measurements). • Take IN life-time = 4 minutes, the totalflux contributed by IN elements is(2.5-3.7)×1025 Mx per day; while assuming NT life-time = 20 hours, the total flux by NT is (2.6-8.0) ×1023 Mx per day.

  24. Life-stories of IN elements

  25. Lifetime distrition for in-elements Mean life-time = 5.8 m. E-fold life time = 3.6 m. Exponential fit (binsize=1min): y=340.3*(e(-x)/3.64)+1.57

  26. More than 10000 IN-elements and 2000 NT-elements are identified. Their magnetic flux and size distributions are derived. • There are plenty of IN ephemeral regions, some of which has total unsigned flux of 1016 Mx and separation < 1 arcsec. • The IN and NT elements have flux distribution function with peak at 1x1016 & 1x1017 Mx, respectively. • IN elements have a life-time of 3-5 minutes, thusly IN fields do contribute the most magnetic flux to the solar surface each day. • The overall relationship among line-of-sight and horizontal magnetic fields, Doppler shifts, and intensity on the quiet Sun and IN elements is complicated. New evaluation needs to be made.

  27. III. Concluding remarks • Some fundamental results from ground-based observations are confirmed • Many things are still not known, say the horizontal fields on the quiet Sun • New quantitative measurements are timely and extremely important; All previous results need to be set on more solid ground • A new era of IN field studies is opening now by Hinode SOT SP/FG observations • More difficult tasks are getting idea on the magnetic coupling in the quiet solar atmosphere

More Related