Magnetic Waves in Solar Coronal Loops Ryan Orvedahl Stony Brook University Advisor: Aad van Ballegooijen Center for Astrophysics

What Heats the Interior? Core ~ 15 MK Proton-proton chain Radiative Zone ~ 5 MK Radiation diffusion Convective Zone ~ 100 kK Bulk fluid motion

What Heats the Atmosphere? Photosphere = ~5700 K Surface that we see Chromosphere = ~ 10 kK Waves? Corona = ~ 1-10 MK Waves? tlight/SunInfo/Transregion.html

Coronal Loops and Alfvén Waves  What are coronal loops?  What are Alfvén Waves?  How do they fit into the model?

Different Temperatures of a Single Active Region  335 Å ~ 2.5 MK 211 Å  ~ 2.0 MK  171 Å ~ 0.6 MK 193 Å  ~ 1.2 MK

Hinode SOT/SP Instrument Solar Optical Telescope and SpectroPolarimeter 0.5 m optical telescope 0.167” res = ~120 km res Zeeman Effect Split energy levels in B field Split ~ B field strength Polarized = how much split

Step 1: Look for the Waves  Loop lifetime ~10-15 min  Ideally want thin loops

Create Movie Hopefully see transverse waves Very small amplitudes Program to measure changes of transverse position with sub-pixel accuracy

Select a Loop  Loop  Follow max intensity over time  Plot position vs time  Ideally want a sinusoidal curve Transverse position:

Best Examples of Alfvén Waves Velocity ~1 km/s

Step 2: Modeling a Single Loop Reflection and nonlinear terms important? Assumptions: Neglect curvature Circular cross section throughout r = r(z) Constant density in cross section ρ = ρ(z) And a few others Calculates heating rate, Q Cor photosphere  Symmetric about apex  TR

How does Q cor depend on B phot ? van Ballegooijen et al varied L cor, B cor Fit equation for Q cor Fine structure in m-gram  various values of B phot

Step 3: Reproduce Fine Structure? Read B z at z = 0 Calculate B (x, y, z) assuming a potential field Trace ~10 8 field lines Estimate Q cor using eqn 3D spatial distribution

Compare to AIA Images Above: ~75 field lines Above: AIA Image taken in 171 Å (~600,000 K) Right: 3D spatial distribution of Q cor M-gram and AIA from same date/time

Magnet AIA Images Quantitative Comparison

Magnet AIA Images

Conclusions What Next? No definitive Alfvén waves Possible disagreement Found Vel ~ 1 km/s Theory ~ 30 km/s Q cor increases with B phot Importance of reflection and nonlinear terms Can reproduce fine structure Bright loops possibly result of small loop length Keep searching increase angular resolution Differentiate between p-mode and Alfvén waves Incorporate: loop motions Interactions between loops Investigate non-potential models

Questions? Thank you to Aad van Ballegooijen Kathy Reeves and all the REU Students for making this both a fun and productive summer