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Judy Karpen Naval Research Laboratory http://solartheory.nrl.navy.mil/ [email protected] Prominence Dynamics: the Key to Prominence Structure. SVST H  image courtesy of Y. Lin. Outline. Constraints on Plasma Structure Plasma Models Levitation Injection

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Prominence Dynamics: the Key to Prominence Structure

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Judy karpen naval research laboratory http solartheory nrl navy mil judy karpen@nrl navy mil

Judy Karpen

Naval Research Laboratory

http://solartheory.nrl.navy.mil/

[email protected]

Prominence Dynamics: the Key to Prominence Structure

SVST H image

courtesy of Y. Lin


Outline

Outline

  • Constraints on Plasma Structure

  • Plasma Models

    • Levitation

    • Injection

    • Evaporation (thermal nonequilibrium)

  • Physics of Thermal Nonequilibrium

  • Implications for Magnetic Structure

  • Crucial Observations by Solar B and STEREO


Plasma structure constraints

Observational

Spine and barbs

Knots and threads

Appearance varies with T

Theoretical

Mass comes from chromosphere

Mass traces magnetic structure (frozen in)

|| >> 

Hg ~ 500 km

Energy input consistent with coronal heating

Plasma Structure: Constraints

10 Mm

Threads: length ~ 25 Mm, width ~ 200 km (SVST, courtesy of Y. Lin)


Plasma is not static model must be dynamic

plasma is NOT static model must be dynamic


Levitation

Levitation

Converging bipoles

Photospheric reconnection site

Cool chromospheric plasma is lifted into the corona by reconnected field lines, during flux cancellation

see Galsgaard & Longbottom 1999, Pecseli & Engvold 2000, Litvinenko & Wheatland 2005


Injection

Injection

corona

photosphere

Photospheric reconnection between arcade and cancelling bipole drives cool, field-aligned jets

see Chae et al. 2004, Liu et al. 2005


Evaporation the thermal nonequilibrium model

Evaporation: the Thermal Nonequilibrium Model

Hypothesis: condensations are caused by heating localized above footpoints of long, low-lying loops, with heating scale  << L

from Tmax to apex: N2(T) L >> Q 

from footpoint to Tmax: N2(T)  ~ Q 

References (all ApJ): Antiochos & Klimchuk 1991; Dahlburg et al. 1998; Antiochos et al. 1999, 2000; Karpen et al. 2001, 2003; Karpen et al. 2005, 2006


Prominence dynamics the key to prominence structure

Why do condensations form?

  • chromospheric evaporation increases density throughout corona increased radiation

  • T is highest within distance ~  from site of maximum energy deposition (i.e.,near base)

  • when L > 8 , conduction + local heating cannot balance radiation near apex

  • rapid cooling  local pressure deficit, pulling more plasma into the condensation

  • a new chromosphere is formed where flows meet, reducing radiative losses


Prominence dynamics the key to prominence structure

Why does thermal nonequilibrium occurwith asymmetric heating?

  • Constraints: P1 = P2 , L1 + L2 = L, E1 E2

  • Scaling Laws: E ~ PV ~ T7/2 L ~ P2 L T-(2+b)

  • Key Result: P ~ E(11+2b)/14 L (2b-3)/14

    • e.g., for b = 1, P ~ E13/14 L -1/14

    • equilibrium position: L1 / L2 = (E1 / E2 ) (11+2b)/(3-2b)

    • for b = 1, L1 / L2 = (E1 / E2 ) 13 !!

    • for b 3/2, no equilibrium is possible


Modeling thermal nonequilibrium

Requirements

1D hydrodynamics

Solar gravity

Coronal heating

Radiation and thermal conduction

Assumptions

One flux tube among many in filament channel

Low plasma  (rigid walls)

Optically thin radiation (no radiative transport)

Volumetric coronal heating localized near footpoints

Simulations:ARGOS, 1D hydrodynamic code with

adaptive mesh refinement (AMR) -- REQUIRED

MUSCL + Godunov finite-difference scheme

thermal conduction, solar gravity, optically thin radiation (Klimchuk-Raymond [T])

spatially and/or temporally variable heating

Modeling Thermal Nonequilibrium

(T)  N2 T-b


1d hydrodynamic equations

1D Hydrodynamic Equations

mass

momentum

energy

ideal gas

“No meaningful inferences on the heating process can be obtained from static models.” - Chiuderi et al. 1981


Initial and boundary conditions

60-Mm chromospheres*

T = 3x104 K

mass source/sink

heat flux sink

maintain correct relationship between coronal pressure and chromospheric properties

Closed ends

v=0, g=0

T=const., dT/ds=0

Nonuniform g||

285-Mm corona

Tapex ~ 3 MK

Napex ~ 6 x 108 cm-3

Uniform small “background” heating

Range of flux tube geometries

Initial and Boundary Conditions

*Note: presence of deep chromosphere strongly influences results (as in 1D loop models)


Shallow dip

Shallow Dip

NRK run


Deep dip

Deep Dip

NLK run


Very shallow dip

Very Shallow Dip

Loop D run


Very shallow arch

Very Shallow Arch

Loop A run


Impulsive heating very shallow dip

Impulsive Heating + Very Shallow Dip

<dt> = 500 s


Impulsive heating very shallow dip1

Impulsive Heating + Very Shallow Dip

<dt> = 2000 s


Steady vs impulsive heating

Condensations always form (for loop length and heating scales used in simulations)

Condensation remains at midpoint and grows unless footpoints are heated unequally

Highly repetitive behavior:

condensation formation times, masses, and lifetimes

adjacent corona can develop periodic unsteady flows

Condensation speeds ~ 10 km/s, faster when falling vertically or a pair is merging

Condensations form if pulses are < 2000 s apart, on average, or if background heating is absent

Shorter pulses cause stronger flows but don’t affect condensing process

Although total energy input at both footpoints is equal, condensations do not always remain static and growing

Entire system is more chaotic, but quasiperiodicities appear at times

Condensation speeds comparable or lower, but motions are much less predictable

Length of condensation varies more; wider range of sizes/masses per run

Steady vs Impulsive Heating


Summary of results

Summary of Results

  • Plasma dynamics provide important constraints on prominence magnetic structure and coronal heating

  • Steady footpoint heating produces no (significant) condensations in

    • Loops shorter than ~8 x heating scale (e.g., overlying arcade)

    • Loops higher than the gravitational scale height

  • No dynamic condensations on deeply dipped loops

  • Long threads only form in highly flattened loops

  • Impulsive heating produces condensations IF

    • Average interval is < radiative cooling time (~2000 s) OR

    • No uniform background heating exists


Where is the plasma in the sheared arcade

Where is the plasma in the sheared arcade?

red = too short

green = too tall

black = too deep

blue = just right


Crucial observations

Crucial Observations

  • STEREO

    • Estimate prominence mass

    • 3D view of plasma dynamics and structure

  • Solar B

    • Proper motions and Doppler signatures of plasma dynamics

    • Origin of filament-channel shear

    • Coronal heating scale, location, variability


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