Magnetic Waves in Solar Coronal Loops

Ryan OrvedahlStony Brook University

Advisor:Aad van

BallegooijenCenter for

Astrophysics

What Heats the Interior?

http://en.wikipedia.org/wiki/Sun

Core ~ 15 MKProton-proton chain

Radiative Zone ~ 5 MKRadiation diffusion

Convective Zone ~ 100 kKBulk fluid motion

What Heats the Atmosphere?Photosphere =

~5700 KSurface that we see

Chromosphere = ~ 10 kKWaves?

Corona = ~ 1-10 MKWaves?

http://solar.physics.montana.edu/YPOP/Spotlight/SunInfo/Transregion.html

Coronal Loops and Alfvén Waves

http://en.wikipedia.org/wiki/Gateway_Arch

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 InstrumentSolar Optical Telescope and SpectroPolarimeter

0.5 m optical telescope0.167” res = ~120 km

res

Zeeman EffectSplit energy levels in B

fieldSplit ~ B field strengthPolarized = how much

split

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

Step 1: Look for the WavesLoop 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 WavesVelocity ~1 km/s

Step 2: Modeling a Single LoopReflection and nonlinear terms

important?Assumptions:

Neglect curvatureCircular cross section throughout

r = r(z)Constant density in cross section

ρ = ρ(z)And a few others

Calculates heating rate, QCor

photosphere

photosphere

Symmetric about apex

TR

TR

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

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 eqn3D spatial distribution

Compare to AIA Images

Above: ~75 field linesAbove: AIA Image

taken in 171 Å (~600,000 K)Right: 3D spatial

distribution of Qcor

M-gram and AIA from same date/time

Mag

net

AIA

Im

ag

es

Quantitative Comparison

Quantitative ComparisonM

ag

net

AIA

Im

ag

es

Conclusions What Next?No definitive Alfvén

wavesPossible disagreement

Found Vel ~ 1 km/sTheory ~ 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

resolutionDifferentiate between p-mode and Alfvén

waves

Incorporate: loop motions Interactions between

loops

Investigate non-potential models

Questions?

Thank you toAad van Ballegooijen

Kathy Reevesand all the REU Students

for making this both afun and productive

summer