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The Internal Rotation of the Sun
Presented by Changyi Tan
11,03,2005
Ⅰ How to observe the interior of the Sun?
1, The method — Helioseismology
Why is Helioseismology? (opaque or
optical thickness)
2, The instrumentations for Helioseismology
Global Oscillation Network Group (GONG)
Michelson Doppler Imager (MDI)
Ⅱ How Helioseismology works?
Basically, observe the surface sound
waves of the Sun. People can get the
coupled multi-modes spherical harmonic
oscillation signals, and separate them to
some normal mode harmonic wave.
There are two kinds of sound waves — p
mode and f mode.
f mode is used to analyze the surface
wave, it propagates on the surface of the
Sun —Photosphere
p mode wave is used to detect the interior of the Sun.
The parameter of p mode wave is l.
The restoring force is pressure gradient .
from http://gong.nso.edu/.
Ⅲ The internal structure of the Sun.
from http://gong.nso.edu/.
We concentrate on the Convection Zone.
The parameters of Convection Zone:
From 0.8 R~ 1 R
Cool temperature~ 106 K
More opaque
High magnetic strength 103~104 Gauss
High density~?
But the density at the top of Convection Zone is
very low ~ 0.0000002 gm/cm³
Ⅳ Dynamo of the convention Zone:
1, Magnetic fields:
The topology of the magnetic fields is very
complicated. Related to the poroidal field
and toroidal field. These relate to the
sunspots , CMEs, flares and so on.
The magnetic pressure and tension should
be stronger than them in the atmosphere.
But the gas pressure should also be
stronger, so β not necessarily be small.
2, Convection:
Cool Temperature➱ Electrons reconbine with other
particles (Ions) and the photons can be easily
absorbed. This decreases the radiative conductivity
and increases the temperature gradient. Where this
occurs a volume of material moved upward will be
warmer than its surroundings and will continue to
rise further. These convective motions carry heat
quite rapidly to the surface. The fluid expands and
cools as it rises. At the visible surface the
temperature has dropped to 5,700 K . The
convective motions themselves are visible at the
surface as ➱ granules and supergranules.
3, Differential Rotation
(a),The different latitude the rotation rate is different.[2]
Tachocline, shear layers
(b), The Meridional Circulation
related to butterfly
(c), Appear quasi-periodic oscillation[1]
Ⅴ,Butterfly
From [2]
☆Physics
Due to the differential rotation, the weak poroidal
field will produce a strong toroidal field below
surface when solar minimum.
Kinks in toroidal field rise to form sunspots at low
latitude.
The leading polarities of south and north of the
equator are due to the Coriolis Force when
toroidal field rises.
At the sun activity minimum, the leading polarity will
reverse. Because the supergranular eddy
diffusion.
From [5]
Kink (from [5])
( From [5] )
Ⅵ The rotation at the deep interior—like a
rigid body
References:
1, Michael J. Thompson et al. Annu. Rev.
Astron. Astrophys. 2003. 41:599-643
2, R. Howe The Internal Rotation of The
Sun, 2003
3, Michael Stix The Sun. 2002
4, Peter A. Gilman, Mark S. Miesch, ApJ,
611:568-574, 2004 August 10
5, E.R. Priest, Solar Physics and MHD,
1981
Thanks a lot.