Magnetosphere (magnetic field)• Convection of liquid metals in the outer core creates

the Earth's magnetic field. • Extends outward from the Earth for several thousand

kilometers• Deflects the Sun's solar wind. Without this field, the

solar wind would directly strike the Earth's atmosphere. This could potentially have removed the Earth's atmosphere, rendering it nearly lifeless, as is hypothesized for Mars.

Earth’s Magnetic FieldEarth is a giant

dipole magnetMagnetic poles

are very close to the geographic poles

May result from different rotation speeds of outer core and mantle

Polar Wandering

The apparent movement was called polar wandering.

The best explanation for this movement is that the poles are stationary, and the continents moved.

In the 1950’s, research showed that the poles had been in differentpositions in the past.

“Polar Wandering”

* Further evidence for plate tectonics

Misnomer - The magnetic poles haven’t moved….the plates have moved.

Magnetic ReversalsEarth’s present magnetic field is called

normal. Magnetic north is near geographic north.

At various times in the past, Earth’s magnetic field has completely reversed, with magnetic south near the north geographic pole. This is referred to as a magnetic reversal.

Magnetic Reverals

• North magnetic pole switches with South magnetic pole

• 4-5 during the last 10 my• No idea when it will flip again

Magnetic Reversals

Measuring paleomagnetism and dating continental lava flows led to the realization that magnetic reversals

existedthe establishment of a magnetic

reversal time scale

- Rapid Rotation- Metal (electrical conductor)

• magnetic field generation requires:

What makes the Earth a magnet?

- Liquid Core

Will a compass lead youdirectly to the geographicNorth Pole???

Van Allen Belts -

• Two regions surrounding Earth that capture high-energy charged particles

• Particles originate in solar wind

a) outer belt - contains mostlylighter electrons

b) inner belt contains heavierprotons

We’d die in the Van Allen Belts

Charged particles escape Van Allen belts near the North and South magnetic poles

Charged particles then collide with air molecules, get excited, then…

=> Produce spectacularlight show called AURORA

“Northern Lights”

more pics