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Hinode/SOT Observations of Quiescent Prominences

Hinode/SOT Observations of Quiescent Prominences. Thomas Berger, T. Tarbell, N. Hurlburt, B. Lites, R. Shine, G. Slater, A.Title, S. Tsuneta, J. Okamoto, K. Ichimoto, Y. Katsukawa, M. Kubo, S. Nagata, T. Shimizu and the rest of the SOT Team. Hinode Overview. SOT Solar Optical Telescope. EIS

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Hinode/SOT Observations of Quiescent Prominences

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  1. Hinode/SOT Observations of Quiescent Prominences Thomas Berger, T. Tarbell, N. Hurlburt, B. Lites, R. Shine, G. Slater, A.Title, S. Tsuneta, J. Okamoto, K. Ichimoto, Y. Katsukawa, M. Kubo, S. Nagata, T. Shimizu and the rest of the SOT Team

  2. Hinode Overview SOT Solar Optical Telescope EIS Extreme Ultraviolet Imaging Spectrometer XRT X-ray Telescope

  3. SOT Overview Introduction Focal Plane Package (FPP) • Optical Telescope Assembly (OTA): • 0.5 m Gregorian Telescope • Built by NAOJ/JAXA/Melco • Focal Plane Package (FPP): • Broadband Filter Imager (BFI) • Narrowband Filter Imager (NFI) • Spectropolarimeter (SP) • Built by Lockheed/HAO • Cameras by E2V/RAL

  4. Introduction • Hinode/SOT images prominences above the solar limb in two wavelengths: • Ca II H-line at 396.8 nm 0.054”/pix • H Balmer Alpha line at 656.3 nm 0.08”/pix • Spatial resolution determined by 2x2 pixel summing. 2-pixel resolution is: • Ca H-line ~ 160 km • H-alpha ~ 230 km • Typical temporal resolution values are 30--60 sec (15--30 sec cadence). • SOT telescope is diffraction limited with no seeing distortions.

  5. Ca II H-line 396.8nm 30-Nov-2006 NW limb 6 hrs.

  6. Sample Regions TS1, TS2 = horizontal time slices Box = averaged vertical time slice

  7. Horizontal Time Slices Oscillations of unknown origin TS2 TS1

  8. Vertical Composite Time Slice 16 1-pixel slices summed horizontally

  9. Vertical Composite Time Slice 16 1-pixel slices summed horizontally 1 2 8 4 7 3 5 6 Downflows Upflows v1 = 8.9 km/s v7 = 9.3 km/s v8 = 8.9 km/s < v > = 9.0 km/s v2 = 12.2 km/s v3 = 19.2 km/s v4 = 12.6 km/s v5 = 11.9 km/s v6 = 8.9 km/s < v > = 12.9 km/s

  10. Example Vortex Closeup Grid = 2” 2.5 Rotations Rate = 3.27 x 10-3 rad/sec ~3000 km diameter

  11. Upflow Plumes Closeup Grid = 2”

  12. Upflow Plume Structure & Velocity Estimates 34 sec between frames 2 1 3 656 658 660 662 664 666 v1 = 7.1 km/s v2 = 14.2 km/s v3 = 19.9 km/s

  13. Upflow Plume Structure & Velocity Estimates 34 sec between frames 3 668 670 672 674 676 678 v3 = 14.4 km/s

  14. Upflow Plume Structure Detail 34 sec between frames 2250 km 7500 km v4 = 26.3 km/s 4 680 682 684

  15. Plume Velocity Measurements v = 23 km/s v = 21 km/s a = -0.18 km/s2 v = 18 km/s v = 23 km/s

  16. Downflow Stream Closeup Grid = 2”

  17. Example Downflow Stream

  18. H-a Line center 656.3nm 25-April-2007 SW limb (rotated) 5 hrs.

  19. Overlay of Ca II H-line on H-alpha

  20. H-alpha 656.3nm 8-Aug-2007 NE limb 4 hrs.

  21. Ca II H-line 396.8nm 16-Aug-2007 NW limb 5 hrs.

  22. H-alpha 656.3nm 16-Aug-2007 NW limb 5 hrs.

  23. Ca II H-line 396.8nm 03-Oct-2007 NW limb 5 hrs.

  24. H-alpha 656.3nm +408 mA 03-Oct-2007 NW limb 408 mA ~ 20 km s-1

  25. Examples of non-plume forming prominences: • Quiescent prominences with little or no discernible vertical motions: • 23 December 2006 • 11-12 July 2007 • 4-5 August 2007 • Active region prominences • 9 November 2006 (Okamoto prominence) • 18 December 2006 • 9 February 2007

  26. Ca II H-line 396.8nm 23-Dec-2006 NW limb 16 hrs. w/gap

  27. Ca II H-line 396.8 nm 12-July-2007 NE limb 4 hrs.

  28. Ca II H-line 396.8 nm 5-Aug-2007 NW limb 6 hrs.

  29. Active Region 10922 Ca II H-line 396.8 nm 9-Nov-2006 W limb 1 hr.

  30. Active Region 10930 Ca II H-line 396.8 nm 18-Dec-2006 W limb 6 hrs.

  31. Active Region 10940 Ca II H-line 396.8 nm 18-Dec-2006 W limb 10 hrs.

  32. Findings • Two appearances of quiescent prominence structures in Hinode/SOT database: • “Sheet” or “Hedgerow” prominences with ubiquitous vertical motion. • “Horizontal” prominences w/ no obvious vertical motion. • Sheet prominences always show the presence of upflow plumes, downflow streams, and large-scale vortices. There is no such thing as a static sheet prominence. • Dark upflow “plumes” are intermittent, < V > ~ 20 km/sec, 10 minute characteristic lifetime, 400 - 700 km width. • Bright downflow “streams”, < V > ~ 10 km/sec, 10 min characteristic lifetime, 250 - 700 km width. • Vortices, characteristic scale 103 km, 3x10-3 rad/sec • Rotational endpoint structures • Bright “support arches” ~5000 km above photosphere • Arches “break” under the weight of accumulated plasma • Horizontalprominences always show horizontal flows on “shorter” disjoint fibrils. • Very little or no vertical motions - “vertically static”. • No obvious plume formation. • All AR prominences seen so far appear “horizontal” in structure.

  33. = Hypotheses • What causes the dark buoyant upflows? • 1. Thermal plume hypothesis: the upflow plumes are caused be localized heatings in the photosphere at the magnetic neutral line. The source of the heating is magnetic reconnection at the cancellation sites of larger magnetic elements. The heating causes a density deficit relative to the surrounding plasma. This causes the heated volume to rise adiabatically in the form of a thermal plume. Flow character is turbulent and does not appear to follow magnetic field lines. The constant rise speed of the plumes implies that the bouyancy force is balanced by fluid dynamic and/or magnetohydrodynamic “drag” forces. Assuming only fluid dynamic drag, a characteristic size R = radius of spherical “bubble”, and a unity drag coefficient:

  34. Using g = 274 m s-2, v = 20,000 km s-1, T = 7000 K, and R = density scale height at T(7000) = 300 km, Hypotheses • 1. Thermal plume hypothesis: (cont.) Assuming a perfect gas in pressure equilibrium Temperature in plumes ~60,000K - sufficiently hot to reduce level populations necessary for scattering of Ca II and H-alpha radiation.

  35. Low & Hundhausen, ApJ, 443, 818, 1995. Hypotheses • 1. Thermal plume hypothesis: (cont.) Note: the foregoing assumes plume kinetic energy density >> magnetic field pressure. i.e. this is a high-Beta plasma “in the corona”. Given the density of prominence plasma (ne ~1011 cm-3), this can only happen where B ~ 0.

  36. Hypotheses • 1. Thermal plume hypothesis: (cont.) A really wild idea: These thermal plumes exist everywhere where there is magnetic reconnection in the lower atmosphere. I.e., the prominence material simply makes the plumes visible by their inability to scatter chromospheric radiation. Either you heard it here first... or I will plausibly deny ever having said this...

  37. Hypotheses • 2. Magnetic Bubble hypothesis: (courtesy B.C. Low) We suppose that magnetic reconnection in the photosphere results in highly evacuated magnetic “bubbles” that rise through the prominence due to the density deficit caused by the magnetic field energy density. In this case, both the Lorentz force and fluid dynamic drag resist the bouyancy force of the “bubble”. The temperature of the bubble remains at ambient temperature. The plumes are dark because the density is so low that chromospheric Ca H-line and H-alpha radiation are no longer efficiently scattered in the plumes. A really wild idea: These magnetic bubbles exist everywhere where there is magnetic reconnection in the lower atmosphere. They are just made visible by prominences... Either you heard it here first... or I will plausibly deny ever having said this...

  38. Coming soon.... • More (better) Doppler velocity measurements in H-alpha. • Many more prominences in Cycle 24 with other instruments! STEREO He II 304Å 22-Sep-2007

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