Supercomputers simulation of solar granulation

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2 Supercomputers simulation of solar granulation simulation by Stein et al (2006), visualization by Henze (2008) Beyond Solar Dermatology But still stops at 0.97R! what lies deeper still?

3 Supercomputers simulation of solar granulation simulation by Stein et al (2006), visualization by Henze (2008) Beyond Solar Dermatology But still stops at 0.97R! what lies deeper still?

4 Giant Cells Eventually the heirarchy must culminate in motions large enough to sense the spherical geometry and rotation radial velocity, r = 0.98R L ~ 100 Mm U ~ 100 m s -1 t ~ days - months

5 Giant Cells Eventually the heirarchy must culminate in motions large enough to sense the spherical geometry and rotation radial velocity, r = 0.98R L ~ 100 Mm U ~ 100 m s -1 t ~ days - months

6 Giant Cells carry energy and redistribute angular momentum That s how the Sun shines (Carrying energy from 0.7R to surface) That s why the equator spins faster than the poles (Only giant cells are big and slow enough to sense the rotation and spherical geometry)

7 Giant cells and the global circulations they produce build magnetic fields The Solar Dynamo

8 Giant cells and the global circulations they produce build magnetic fields The Solar Dynamo

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11 2 The Solar Dynamo Building magnetic fields by means of turbulent convection, shear, magnetic buoyancy and global circulations 1 3 4

12 2 The Solar Dynamo Building magnetic fields by means of turbulent convection, shear, magnetic buoyancy and global circulations 1 3 4

13 Why 11 years? Some solar dynamo models suggest that a slow equatorward flow near the bottom of the convection zone may regulate the cycle period How slow? 2 m/s (5 mph) gets you from the pole to the equator in 11 years!

14 Simmering below the Surface The structure of the solar interior Sphere No. 6 (Sphere Within a Sphere) Arnaldo Pomodoro Hirshhorn Museum and Sculpture Garden Washington, DC

15 We are now in the deepest solar minimum of the space age!

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27 Alfven s Theorem (flux freezing) In the perfectly conducting limit (η= 0), the flow can t cross magnetic field lines Corona magnetic energy >> kinetic energy flow follows field coronal loops! Convection Zone magnetic energy << kinetic energy flow pushes field around dynamo!

28 Alfven s Theorem (flux freezing) In the perfectly conducting limit (η= 0), the flow can t cross magnetic field lines Corona magnetic energy >> kinetic energy flow follows field coronal loops! Convection Zone magnetic energy << kinetic energy flow pushes field around dynamo!

29 Alfven s Theorem (flux freezing) In the perfectly conducting limit (η= 0), the flow can t cross magnetic field lines Corona magnetic energy >> kinetic energy flow follows field coronal loops! Convection Zone magnetic energy << kinetic energy flow pushes field around dynamo!

30 Magnetic Reconnection Violation of Alfven s Theorem Reshapes magnetic Topology Releases Energy Accelerates Particles (important for solar flares) Zweibel & Yamada (2009)

31 Helioseismology Metcalfe

32 Differential Rotation P ~ 35 days P ~ 27 days

33 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ P ~ 27 days

34 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone P ~ 27 days

35 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone Convection Implicated as source of DR P ~ 27 days

36 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone Convection Implicated as source of DR Nearly radial contours at midlatitudes in CZ P ~ 27 days

37 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone Convection Implicated as source of DR Nearly radial contours at midlatitudes in CZ P ~ 27 days Radial Ω gradients near top & bottom: Tachocline Near-surface shear layer

38 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone Convection Implicated as source of DR Nearly radial contours at midlatitudes in CZ P ~ 27 days Radial Ω gradients near top & bottom: Tachocline Near-surface shear layer Interior rate intermediate between equator & poles in CZ

39 Differential Rotation P ~ 35 days Monotonic decrease in Ω of ~30% from equator to high latitudes in CZ Nearly uniform rotation in radiative zone Convection Implicated as source of DR Nearly radial contours at midlatitudes in CZ P ~ 27 days Radial Ω gradients near top & bottom: Tachocline Near-surface shear layer Interior rate intermediate between equator & poles in CZ Persistent in time

40 Meridional Circulation Hathaway & Rightmire 2010 Observational techniques Local helioseismology (left and below) Surface Doppler measurements (right) Feature Tracking Ulrich Systematically poleward at mid latitudes near surface (r > 0.95R) Much weaker that differential rotation (~ 20 m/s) Variable in time...and that s about all we know! Zhao et al 2013

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