Beijing UniversityTuesday 18-May-2010 Quiescent Prominence Instabilities Hinode/SOT and AIA Explorations Thomas Berger Lockheed Martin Solar and Astrophysics Lab

Hinode 2nd Science MeetingWednesday 01-Oct-2008 Klyuchi Russia 1-Aug :22:

Hinode 2nd Science MeetingWednesday 01-Oct-2008 Two types of prominences 1. Active Region Prominences Motions along primarily horizontal threads only Very active/eruptive Not associated with large coronal cavities

Hinode 2nd Science MeetingWednesday 01-Oct-2008 Two types of prominences 2. Quiescent Prominences Motions along primarily vertical threads Not very active/ eruptive Associated with large coronal cavities Subject to buoyant instabilities

Hinode 2nd Science MeetingWednesday 01-Oct-2008 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 2nd Science MeetingWednesday 01-Oct-2008 Hinode/SOT offers some clues... Ca II H-line nm 90W 52N 17 sec cadence

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 SOT H-alpha 08-Aug-2007

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 S max = 17.8 km s -1 Speed and Area vs. Time for 08-Aug-2007 plume

Beijing UniversityTuesday 18-May-2010 SOT H-alpha 25-Apr-2007

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 S max = 30.1 km s -1 Speed and Area vs. Time for 25-Apr-2007 plume

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May April-2007 MSDP MeudonSOT H-alpha Prominence observed in the H a line center by the MSDP spectrograph (left ) and by Hinode SOT (ri g ht ) 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.

Beijing UniversityTuesday 18-May-2010 Common denominator: plumes form from a dark “cavity” rising into the prominence from below SOT H-alpha 08-Aug-2007

Beijing UniversityTuesday 18-May-2010 Common denominator: plumes form from a dark “cavity” rising into the prominence from below SOT Ca II H 30-Nov-2006

Beijing UniversityTuesday 18-May km sec km sec km sec -1 Time slice through 08-Aug-2007 plume

Beijing UniversityTuesday 18-May-2010 SOT Ca II H-line 16-Aug-2007

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 Large Bubble Growth Rate

Beijing UniversityTuesday 18-May-2010 Large Bubble Growth Rate Time, 1000 sec Area, 10 6 km 2 A = t + 6.6t 2

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 III. Relation of Prominences to Coronal Cavities

Beijing UniversityTuesday 18-May-2010

Beijing UniversityTuesday 18-May-2010 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 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.

Beijing UniversityTuesday 18-May-2010 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.

Beijing UniversityTuesday 18-May-2010 Quiescent prominences appear static in low resolution data but they are in a constant balance between gravitational drainage and upwelling from below.

Beijing UniversityTuesday 18-May-2010 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-B 195 Negative Hinode SOT H-alpha

Beijing UniversityTuesday 18-May-2010 Hinode SOT H-alpha Erupted prominence remnant region 20-Jul-2008

Beijing UniversityTuesday 18-May-2010 MLSO PICS H-alpha 8-Nov-2007

Beijing UniversityTuesday 18-May Mm Mm Mm :0118:1118:20 18:2918:3818:50 18:5919:0819:17

Beijing UniversityTuesday 18-May-2010 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: ~ km larger bubbles: 2--4 Mm

Beijing UniversityTuesday 18-May-2010 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?

Beijing UniversityTuesday 18-May-2010 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...

Beijing UniversityTuesday 18-May-2010 Some numbers... “Standard quiescent prominence characteristics (Hirayama’s numbers): Temperature T 0 = 7000 K Electron density n e0 = 8.4e10 cm -3 Ionization fraction f 0 = 0.3 He/H ratio = 0.1 Pressure P 0 = 0.06 dyne Mass density μ 0 = g cm -3 Viscosity ν 0 = poise (H at 7000K) Magnetic Flux density = 30 gauss (Casini et al ) Plume characteristics: L 1 = widest width = 4 Mm H 1 = height = 15 Mm v 1 = 15 km s -1 Then: Alfven speed = 85 km s -1 (~6 times plume speed) Magnetic Reynolds Number Rm ~10 33

Beijing UniversityTuesday 18-May-2010 Some numbers (cont.)... Rayleigh-Taylor instability: Atwood number A = (1 - η)/(1+η) where η = ρ low /ρ high A→1: lighter fluid penetrates heavier fluid above in form of small bubbles A→0: system of symmetric plumes/fingers and downflowing “spikes” Since prominence plumes are closer to bubble form and there is little evidence of spikes (at the source region interface), assume A ~ Then: Density of plume fluid ρ 1 = 1.5e-10 g cm -3 Reynolds number of the flow Re = ρ 1 L 1 v 1 /μ 0 ~ 10,000 Plume mass = ρ 1 V 1 (where V 1 = volume of plume = h max t, t = 1000 km) ~ 900 kg/plume ≅ 0.07% of prominence mass Plume interval = 500 s → replacement of all prominence mass in ~50 days

Beijing UniversityTuesday 18-May-2010 Atmospheric Imaging Array (AIA) The Solar Dynamics Observatory (SDO) Dr. Thomas Berger Lockheed Martin Solar & Astrophysics Lab