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Magnetic Storm Notes

Magnetic Storm Notes. www.scifun.ed.ac.uk. Why Earth has a Magnetic Field. Dynamo Effect Earth’s Core contains molten metal (iron and nickel – ferromagnetic!) that circulates (due to convection currents) Circulating Metal causes Electric Currents Magnetic Field. http://geomag.usgs.gov.

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Magnetic Storm Notes

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  1. Magnetic Storm Notes www.scifun.ed.ac.uk

  2. Why Earth has a Magnetic Field Dynamo Effect Earth’s Core contains molten metal (iron and nickel – ferromagnetic!) that circulates (due to convection currents) Circulating Metal causes Electric Currents Magnetic Field http://geomag.usgs.gov

  3. Earth’s Core http://geomag.usgs.gov http://www.magnet.fsu.edu

  4. Why is Earth’s Magnetic Field Important? Our magnetic field protects the Earth from space weather/solar storms – the solar wind Protects atmosphere from being blown away Protects us from solar radiation Protects electronics used for communication and our power grid from being disrupted/destroyed http://www.suntrek.org

  5. Evidence of Changes to Earth’s Magnetic Field Evidence: Rocks on either side of the mid ocean ridge, ice cores, hardened lava in Hawaii and Oregon, ancient clay pots, ship’s log books Iron in molten rock lines up in the direction of Earth’s magnetic field – when it cools into rock it leaves a record of Earth’s magnetic field Rocks have shown evidence of changes in Earth’s magnetic field strength and reversals in the field direction

  6. Evidence From Clay Pots This graph shows the strength of the magnetic field as seen in ancient clay pots NOVA

  7. Steens Mountain, Oregon 16 million years ago there was a series of volcanic eruptions while the Earth was in the middle of a magnetic flip. At the beginning of the reversal the field strength decreased 80-90%. The field was originally pointing south and after 300 years it pointed north and the field began to regain strength. This polarity didn’t last and the field started to reverse again During this reversal there was a lower field intensity for 3000 years The field that was left was changing very quickly…

  8. Steens Mountain, Oregon “And what we found was even harder to believe. The quickly chilled margins in the bottom and the top had one direction, like that of the underlying flow, and the middle portion had a direction that was sixty degrees farther away. It was just as though, while the flow cooled, the field had moved sixty degrees, which if you calculate it out, that comes to about six degrees of movement per day. If we were observing this with a compass, you would be able almost to see the motion with your eye. It was truly astonishing and extraordinary.” ROB COE (University of California, Santa Cruz) in NOVA: Magnetic Storm

  9. Magnetic Reversals Causes: disturbances in the field happen occasionally – called instabilities. - Possibly due to anomalies (changes) in the motion of the molten material in the core. - On rare occasions the instabilities can cause a reversal. - Instabilities cause the field to weaken

  10. Last flip about 780,000 years ago – generally flip every 200,000 years (book says a million years) Happened 400 times in the last 330 million yearsTime for flip? – we are overdue Is the field weakening? (10% weaker than in 1845) Is this evidence of a flip in the near future? http://www.pbs.org/wgbh/nova/magnetic/timeline.html

  11. Magnetic Reversals Computer models show multiple poles and a weaker field http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm

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