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

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

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

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

Symmetrical Simulation

Asymmetrical Simulation

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

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?

Projection Effects: Symmetrical

Projection Effects: Asymmetrical

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

6/7 Dec 2010

7 Mar 2011

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

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

2010 Event Symmetric CaseAsymmetric Case

2011 Event Symmetric CaseAsymmetric Case

Results (AIA Only) Event loops traced 8 loops match simulations 8:1 – 5 loops 4:1 – 2 loops 2:1 – 1 loop Event 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.

Rotation To Stereo

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

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

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.

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

Loop Unable to Fit (Kink)

HMI Magnetograms 6 Dec Mar 2011