Beijing UniversityTuesday 18-May-2010 Quiescent Prominence Instabilities Hinode/SOT and AIA...

Beijing University Tuesday 18-May-2010

Quiescent Prominence InstabilitiesHinode/SOT and AIA Explorations

Thomas BergerLockheed Martin Solar and Astrophysics Lab

Hinode 2nd Science Meeting Wednesday 01-Oct-2008

Klyuchi Russia1-Aug-2008 10:22:12.000http://www.zam.fme.vutbr.cz/~druck/eclipse/


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Two types of prominences

1. Active Region Prominences

• Motions along primarily horizontal threads only

• Very active/eruptive

• Not associated with large coronal cavities


Two types of prominences 2. Quiescent Prominences

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• Motions along primarily vertical threads• Not very active/ eruptive• Associated with large coronal cavities

• Subject to buoyant instabilities


Two primary questions regarding quiescent prominences

1. Where does the prominence mass come from?

• Coronal condensation from the cavity or PCTR?

• Footpoint siphon flows due to thermal instability?

2. What causes QPs to erupt?

• Breakout model due to shearing motions?

• Buoyant eruption of the cavity/streamer system?

(50% of CMEs are from QP systems)




Hinode/SOT offers some clues...

Ca II H-line 396.8 nm 90W 52N 17 sec cadence


SOT H-alpha08-Aug-2007


Smax = 17.8 km s-1

Speed and Area vs. Time for 08-Aug-2007 plume




SOT H-alpha25-Apr-2007


Smax = 30.1 km s-1

Speed and Area vs. Time for 25-Apr-2007 plume


25-April-2007

MSDP Meudon SOT H-alpha

Prominence observed in the Ha line center by the MSDP spectrograph (left ) and by Hinode SOT (right ) on 2007 April 25 at 13:19 UT. On the SOT image we have overlaid the contour of the MSDP observation and indicated points where the opacity has been computed using MSDP and HSFA spectra.

Heinzel, Schmieder, et al., ApJ 686, 1383, 2008.


Common denominator: plumes form from a dark “cavity” rising into the prominence from below

SOT H-alpha08-Aug-2007


Common denominator: plumes form from a dark “cavity” rising into the prominence from below

SOT Ca II H30-Nov-2006




SOT Ca II H-line16-Aug-2007


Facts:

• Dark (in visible light) buoyant cavity rises from below into prominence.

• Boundary of the cavity develops perturbations that grow into plumes.

• Plumes rise with nearly constant speed (force balance) to equilibrium heights of 10--20 Mm.

• During ascent, plumes develop Kelvin-Helmholtz instabilities (turbulent mixing).

Hypothesis:

• Plumes are generated by a Rayleigh-Taylor buoyancy instability (aka “Ballooning mode instability”).

• Magnetic field provides tension force analogous to surface tension in fluid dynamics RT instability.


Implications:

• Plumes transport mass and momentum to the prominence above: A significant additional mass source for QP systems has been discovered.



NAVE correlation tracking code courtesy of J. Chae.


Quiescent prominences appear static in low resolution data but they are in a constant balance between gravitational drainage and upwelling from below.


Implications:

• Plumes transport mass and momentum to the prominence above: A significant additional mass source for QP systems has been discovered.

• Larger prominence cavities can reach the coronal cavity above: Prominence cavities may be adding mass, magnetic flux, and helicity to coronal cavities thus bringing them closer to the energetic threshold for buoyant eruption.

STEREO-B195 Negative

Hinode SOTH-alpha


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MLSOPICS H-alpha8-Nov-2007


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Conclusions

• Turbulent upflow plumes provide both mass and upward momentum transfer to the prominence, providing a mechanism to keep prominence gas aloft against the constant gravitational draining.

• Turbulent upflow plumes generate from dark “cavities” that grow into prominences from below

• The cavity boundaries go unstable in a magnetic Rayleigh-Taylor instability mode to create the plumes.

• Cavities can sporadically “re-inflate” with frequencies of ~500 sec and for periods on the order of hours.

• Characteristic wavelength of the RT instability is scale-dependent

• smaller source regions: ~200--300 km

• larger bubbles: 2--4 Mm


• What is the source of prominence cavity buoyancy?

Are the plumes a low or high beta phenomenon?

Are we observing a current sheet below the coronal cavity where

the field is extremely weak (high-beta conditions)?

Questions

Magnetic flux emergence below the prominence?

Thermal impulse from reconnection at the neutral line?

• What is the thermal structure of QPs?

• What is the magnetic configuration in the visible QP region?

Is the prominence-corona transition region a sheath around the QP?

Is the PCTR micro-scaled on threads within the QP?


Speculations...

• Scale dependency of prominence instabilities is related to the prominence magnetic field strength:

• stronger fields impart higher “surface tension”.

• more surface tension allows “bubbles” to grow larger before popping.

• Quiescent prominences exist in current sheets below coronal cavity magnetic flux ropes. In this current sheet, magnetic field is being continually destroyed and the dynamics we observe are enabled by very low field strengths in this region.

Courtesy Yuhong Fan

The future...


Atmospheric Imaging Array (AIA)The Solar Dynamics Observatory (SDO)

Dr. Thomas BergerLockheed Martin Solar & Astrophysics Lab

Beijing UniversityTuesday 18-May-2010 Quiescent Prominence Instabilities Hinode/SOT and AIA...

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