Vincent Surges Advisors: Yingna Su Aad van Ballegooijen

1. Observations and Magnetic Field Modeling of a flare/CME event on 2010 April 8 Vincent SurgesAdvisors:Yingna SuAad van Ballegooijen

2. 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

3. Magnetic Reconnection In Solar Eruptions Stressed coronal magnetic field Relieved by restructuring field lines = lower energy Previously trapped energy converted: kinetic thermal

4. Motivation for research Why study solar eruptions? 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 -Impact on space weather -Potentially dangerous: • Emits energy/radiation • Problems on Earth • Dangers in space Active area of research!

5. 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

6. AIA 193

7. 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)

8. 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- • Flux rope reaches equilibrium • Flux rope erupts as flare/CME

9. Five Models After Relaxation • Step 1: Find threshold

10. Five Models After Relaxation • Step 1: Find threshold • Threshold:

11. 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

12. Finding Best-Fit Model Step 3: Analyzing Comparisons • Model must fit observed loops • Expect to be stable () • Did not use since value >> threshold

13. 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

14. Unstable Model Model 2: • Flux rope continues expanding during relaxation

15. Different Segments of Flux Rope

16. 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.

17. A Special Thanks to Dr. Yingna Su Dr. Aad van Ballegooijen Solar Stellar X-Ray Group Harvard-Smithsonian Center for Astrophysics National Science Foundation