Astronomy Picture of the Day 11-25-02

NASA ^ | 11-25-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2002 November 25

The Earth's Magnetic Field
Credit & Copyright: Gary A. Glatzmaier (UCSC)

Explanation: Why does the Earth have a magnetic field? The electrical conductivity of the molten plasma of the Earth's core should be able to damp the current magnetic field in only thousands of years. Yet our five billion year old Earth clearly causes magnets to point to (defined) north. The mystery is still being studied but recently thought related to motions in the Earth's liquid outer core. Specifically, as portions of the outer core cool and fall inward, oceans of the liquid iron-rich magma rise outward, forced into a helical motion by the spin of the Earth. This motion, many geologists now believe, regenerates Earth's magnetism. Pictured above, a computer simulation shows the resulting magnetic field lines out to two Earth radii, with blue lines directed inward and yellow lines directed outward.

[petuniasevan]

Without a magnetic field we would be vulnerable to greatly increased solar radiation reaching the Earth's surface.

[petuniasevan]

[Graewoulf]

Thanks for the ping!

Where is the surface of the Earth's magnetic field? Is it in the Mantle, between the base of the Mantle and the Outer Core, or in the Outer Core?

[RightWhale]

Where is the surface of the Earth's magnetic field?

What do you mean by "surface" in this case?

[Mr. K]

Everyone is always talking about the magnetic field, but no one does anything about it...

[RightWhale]

I'm starting to think the earth's magnetic field is due to rotation and circulation of the atmosphere, which in turn is due to solar heating and the Coriolis effect.

[boris]

The notion that there is plasma at the core of the Earth astounds me.

What is the current thinking of real, live physicists on this extraordinary proposition?

--Boris