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The Sun’s Magnetic Field
Rotation of the Sun
Rotates on its axis at different rates.
– Sun is gas and plasma, so parts spin at different rates.
Sunspot observations can tell how quickly the surface is rotating.
– Equatorial region = once every 25 days.
– Polar rate = once every 36 days.
The interior does not spin the same way as the surface.
– Belief is the inner regions (core and radiative zone) rotate
more like a solid body.
From the convective zone outward, rotation varies with latitude.
• Tachocline is the boundary between the inner
parts that spin together and the outer parts that
spin at different rates .
• The behavior of the magnetic field is strongly
affected by the combination of convective
currents, (move charged plasma from deep
within) to the surface, with its different rotation.
• Differential rotation is apparently the main driver
of the 11-year sunspot cycle and the associated
22-year solar cycle.
Sun’s Magnetic Field
Large, complex magnetic field extends far out into space.
– called the Interplanetary Magnetic Field (IMF).
– solar wind = stream of charged particles flowing
outward from the Sun, carries the IMF to the
planets and beyond.
– solar wind and IMF interact with planetary
magnetic fields in complex ways, generating
phenomena such as the aurora.
The basic shape of the Sun's magnetic field is like the shape
of Earth’s magnetic field.
active regions are places where the magnetic field is especially strong
and often produces sunspots.
Disruptions in magnetic fields near active regions can cause
explosions on the sun such as solar flares and Coronal Mass
Ejections.
• Some of the Sun's magnetism may even be a
remnant from the primordial cloud from
which the sun formed.
• Solar prominences are visible indicators of
material flowing along magnetic field lines
which arc thousands of kilometers above the
Sun's surface.
Solar Poles
• Like Earth, the sun has a North Pole, a South Pole, and an
equator.
• About every 11 years, the sun's magnetic poles flip - North
becomes South and vice versa.
• This flip happens around the peak of the sunspot cycle.
– Earth's magnetic poles sometimes flip, too. However, it is usually
many thousands to millions of years between flips.
• Sunspots only appear near the Sun's equator, between about
40° North and 40° South latitude.
• Atmosphere at the poles is also different from
the atmosphere above the equator. The
corona sticks out further from the sun's
surface near the equator.
• Solar wind is different at the poles. It "blows"
much faster above the poles than it does
above the Sun's equator