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Magnetic Waves in Solar Coronal Loops

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.

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Magnetic Waves in Solar Coronal Loops

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

  2. What Heats the Interior? • Core ~ 15 MK • Proton-proton chain • Radiative Zone ~ 5 MK • Radiation diffusion • Convective Zone ~ 100 kK • Bulk fluid motion http://en.wikipedia.org/wiki/Sun

  3. What Heats the Atmosphere? • Photosphere = ~5700 K • Surface that we see • Chromosphere = ~ 10 kK • Waves? • Corona = ~ 1-10 MK • Waves? http://solar.physics.montana.edu/YPOP/Spotlight/SunInfo/Transregion.html

  4. Coronal Loops and Alfvén Waves • What are coronal loops? • What are Alfvén Waves? • How do they fit into the model? http://en.wikipedia.org/wiki/Gateway_Arch

  5. 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

  6. 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 http://en.wikipedia.org/wiki/File:Zeeman_effect.svg

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

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

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

  10. Best Examples of Alfvén Waves Velocity ~1 km/s

  11. Step 2: Modeling a Single Loop photosphere • 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, QCor  TR • Symmetric • about apex  TR photosphere

  12. How does Qcor depend on Bphot? • van Ballegooijen et al. 2011 varied Lcor, Bcor • Fit equation for Qcor • Fine structure in m-gram  various values of Bphot

  13. Step 3: Reproduce Fine Structure? • Read Bz at z = 0 • Calculate B (x, y, z) assuming a potential field • Trace ~108 field lines • Estimate Qcor using eqn • 3D spatial distribution

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

  15. Quantitative Comparison Magnet AIA Images

  16. Quantitative Comparison Magnet AIA Images

  17. Conclusions What Next? • No definitiveAlfvén waves • Possible disagreement • Found Vel ~ 1 km/s • Theory ~ 30 km/s • Qcor increases with Bphot • 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

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

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