Will it Fit? A Comparison of Asymmetric Magnetic Reconnection Models and Observations

1. Will it Fit?A Comparison of Asymmetric Magnetic Reconnection Models and Observations Drake Ranquist Brigham Young University Advisors: Mari Paz Miralles and Nick Murphy 2012 SAO Solar REU

2. Magnetic Reconnection • Occurs in highly conducting plasmas when magnetic fields are oriented in opposite directions • Observed in Plasma Experiments, Earth’s Magnetosphere, and the Sun’s Corona • Responsible for energy release and topology changes during solar eruptions

3. Solar Flares and CMEs • The standard model of solar eruptions includes: • Rising plasmoid contained by flux ropes • X-line and current sheet where magnetic reconnection occurs • Inflow and outflow at X-line • Hot, bright post-flare loops • Locations where loops meet the photosphere are called footpoints

4. NIMROD Code • Stands for “Non-Ideal Magnetohydrodynamics with Rotation and Other Doohickies” • Magnetohydrodynamics (MHD) describes macroscopic behavior of conducting fluids like plasmas using Maxwell’s equations and standard fluid hydrodynamics • Solutions represented as sums of finite element basis functions • Includes resistivity and anisotropic thermal conduction • Conducting wall boundary conditions that represent the photosphere

5. Symmetrical Simulation

6. Asymmetrical Simulation

7. Observational Signatures of Asymmetric Reconnection • Distortion of post-flare loops • Asymmetric footpoint motions and brightness • Location of X-line and flow stagnation point • Different inflow velocities • Drifting of the CME current sheet • Circulation within the rising flux rope

8. Questions • Can we find evidence of asymmetric reconnection in observations? • How well do the post-flare loops from the simulations agree with the observations? • Can we determine the ratio of magnetic field strengths on the two sides of an observed post-flare loop?

9. Projection Effects:Symmetrical

10. Projection Effects:Asymmetrical

11. Observations: Two Events • 6/7 Dec 2010 and 7 Mar 2011 • Primary Instruments: • Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) • SECCHI EUVI on STEREO-A and STEREO-B • Both events have a candle-like cusp at shorter wavelengths

12. 6/7 Dec 2010

13. 7 Mar 2011

14. Tracing Loops • Choose loop to fit and trace it by clicking mouse and saving X and Y coordinates

15. Matching Simulations • We assumed that the footpoints of the trace and the simulation had to be at the same location • Magnetic field lines tied to solar surface • Important to know exact location of footpoints • Can automatically scale, center, and rotate simulation about the Z axis • Only free parameters are: • Rotation about the baseline • Loop height • Magnetic field asymmetry

16. 2010 Event Symmetric Case Asymmetric Case

17. 2011 Event Symmetric Case Asymmetric Case

18. Results (AIA Only) • Event 2010 • 12 loops traced • 8 loops match simulations • 8:1 – 5 loops • 4:1 – 2 loops • 2:1 – 1 loop • Event 2011 • 7 loops traced • 6 loops match simulations • 4:1 – 3 loops • 2:1 – 1 loop • 1.5:1 – 1 loop • 1.25:1 – 1 loop These are the best fits in the AIA data, but not the only possible fits. Rotation into STEREO further constrained results.

19. Rotation To Stereo

20. Problems • Simulations are Two Dimensional • Doesn’t allow for more complicated 3-D structure • Simulated loops are isolated • Difficult to trace loops • They split, merge, and twist • Footpoints often saturated giving greater error to location

21. Conclusions • The simulations are able to fit most observations • This technique can be used to get a rough estimate on magnetic field asymmetries • The 6/7 Dec 2010 event is consistent with a magnetic field asymmetry of 4:1 • The 7 Mar 2011 event is consistent with a magnetic field asymmetry of around 1.5:1

22. Future Work • Use same process for other events • See if HMI Magnetograms and potential field models indicate similar asymmetries • Determine error on tracing loops (especially with the footpoint locations) • Look for other observational signatures of asymmetrical reconnection and compare them to these results.

23. Acknowledgements • Advisors Mari Paz Miralles and Nick Murphy • Harvard-Smithsonian Solar REU Program • NSF Grant that supports the REU Program • ATM-0851866 • Ed DeLuca, Kathy Reeves, EMS crew, Hospital Staff, my Parents, and everyone else that kept me alive

25. Loop Unable to Fit (Kink)

26. HMI Magnetograms 6 Dec 2010 7 Mar 2011