Vincent Surges

Advisors:Yingna Su

Aad van Ballegooijen

Observations and Magnetic Field Modeling of a

flare/CME event on 2010 April 8

Solar Eruptions include…

• Coronal Mass Ejections (CME)

• Prominence Eruptions

• Solar Flares

Notable Common Features

-Often occur in the Sun’s active regions

-All involve sudden release of massive energy

-All powered by same physical process

Magnetic Reconnection

In Solar EruptionsStressed coronal magnetic field

Relieved by restructuring field lines

= lower energy

Previously trapped energy converted:

• kinetic

• thermal

Motivation for research

Why study solar eruptions?

-Impact on space weather

-Potentially dangerous:

• Emits energy/radiation

• Problems on Earth

• Dangers in space

Active area of research!

Overview of My Project• Modeling flare/CME event in AR 11060

from 2010 April 8 at ~02:30 UT

• Two models created

1) best-fit NLFFF model prior to eruption

• Accomplished using Coronal Modeling System (CMS) to match coronal loops with created field lines

2) Unstable model of magnetic field during event onset

• Compared with flare footpoints and ribbons at event onset

Instruments

Solar Dynamics Observatory

• Atmospheric Imaging Assembly (AIA) 7 EUV and 3 UV-visible channels Four telescopes

• Helioseismic and Magnetic Imager (HMI) Measures magnetic field strength in

photosphere

Hinode

• X-Ray Telescope (XRT) Soft X-ray images reveal magnetic field

configuration Observe the energy buildup, storage,

and release process in the corona

AIA 193

MHD and Nonlinear Force-Free Fields

Equation of Motion:

In static equilibrium:

Force-Free condition:

One Solution

Assume (current free)

Potential field:

No free magnetic energy in potential field!

Potential field does not match observations

Different solution

Assume

Nonpotential field:

Free energy = nonpotential - potential

in a nonpotential field:

- Constant along field lines

1) α=0 Potential Field

2) α=constant Linear Force-Free Field

3) α=α(r) Nonlinear Force-Free Field (NLFFF)

Creating NLFFF models using CMS

Flux Rope Insertion Method• Construct potential field of region• Create cavity - Insert bundle along path• Two parameters: Poloidal = twist

Axial = shear

• Allow flux rope to relax

Magneto-frictional Relaxation

-Expands flux rope using artificial friction

Two Possibilities-

1) Flux rope reaches equilibrium

2) Flux rope erupts as flare/CME

Five Models After Relaxation

• Step 1: Find threshold

Five Models After Relaxation

• Step 1: Find threshold

• Threshold:

Observing Coronal Loops

• Step 2: Locate observed loops

Loop 1 from AIA 171

Loop 2 from AIA 193

(plotted on AIA 171)

Loops 3, 4, 5 from XRT

• •

Finding Best-Fit Model

Step 3: Analyzing Comparisons Model must fit observed loops Expect to be stable ( )

Did not use since value >> threshold

Loop 1 Loop 2 Loop 3 Loop 4 Loop 5

0.0032 0.0029 0.0035 0.0014 0.0033

0.0024 0.0027 0.0007 0.0003 0.0011

0.0022 0.0041 0.0004* 0.0011 0.0004

0.0026* 0.0082 0.0005* 0.0029 0.0006

Best Model Prior to Eruption

Observing best-fit model:

• Modeled field lines extend higher in (b) due to shorter observed loops• Closely matched observed loops + low AD value = Excellent model

Unstable Model

Model 2:

• Flux rope continues expanding during relaxation

Different Segments of Flux Rope

Summary/Future Work

Our best-fit pre-flare NLFFF ( ) contains a highly sheared and weakly twisted flux rope.

The axial flux in the pre-flare model is close to the threshold ( ).

The unstable model ( ) matches the observations at the early phase of the flare.

All these results strongly support that this event is due to the loss-of-equilibrium mechanism.

Use the unstable model as initial conditions for full 3D-MHD simulations of the observed CME event.

Applying this method to more events.

A Special Thanks

to

Dr. Yingna Su

Dr. Aad van Ballegooijen

Solar Stellar X-Ray Group

Harvard-Smithsonian Center for Astrophysics National Science Foundation