Geomagnetism

The Physics Hypertextbook™
© 1998-2008 by Glenn Elert -- A Work in Progress
All Rights Reserved -- Fair Use Encouraged

prev | up | next

---

Discussion

geomagnetism

This section is intended to be a discussion of magnetism on the large scale, not limited to the magnetic field of the earth (although that will be its primary focus). Perhaps this section should be title "megamagnetism".

start on the surface

The earth's magnetic poles are near but not on the geographic poles.
The south magnetic pole is currently about one hundred kilometers north of Canada in the Arctic Ocean.	The north magnetic pole is currently about one hundred kilometers north of eastern Antarctica in the Pacific Ocean.

work your way down into the earth

• magnetic axis and geographic axis aren't aligned
• gradual drift of magnetic field
• source of geomagnetism is convection of charged outer core
• inner core is hotter than Curie temperature
• inner core spinning faster than earth
• field reversals on a time scale between human and geologic, something like the time scale between ice ages, but episodic not periodic
• geomagnetodynamics

then work your way out into space

[magnify]

The effective reach of a celestial body's magnetic field is known as its magnetosphere. The earth's magnetosphere is compressed on one side and stretched out on the other by the solar wind. It extends about ten earth radii towards the sun and a thousand away from it.

• magnetosphere
• magnetopause
• current sheet comes from the downwind portion of the magnetosphere
• van allen radiation belts
• aurora

Space weather

Real-time space weather information from the Space Environment Center of the US National Oceanographic and Atmospheric Administration (NOAA)
What's the weather like in space right now? Space weather is described by fluctuations in the earth's magnetic field and the speed and pressure of the solar wind. Values in the red indicate a geomagnetic storm is underway.
Current auroral activity in the northern and southern hemispheres. (The red arrow points toward the sun.)
The K Index. This graph shows the overall deviation of the earth's magnetic field for the last two to three days. Values in the red (K > 4) indicate a geomagnetic storm.

keep going out to the sun, then work out from the sun to the edge of the solar system

• sunspots are magnetic storms, sunspots always occur in pairs
• termination shock
• heliopause
• bow shock

end with the galactic magnetic field

Summary

• bullet

Problems

practice

1. Write something.
   • Answer it.
2. Write something.
   • Answer it.
3. Write something.
   • Answer it.
4. Write something.
   • Answer it.

numerical

1. problems

Resources

• general
  • Exploration of the Earth's Magnetosphere, David P. Stern & Mauricio Peredo, NASA
  • Earth's Inner Core Rotating Faster than Planet, Paul G. Richards, Lamont-Doherty Earth Observatory, February 2000
  • High frequency Active Auroral Research Program (HAARP)
  • International Solar-Terrestrial Physics Program (ISTP)
  • North Magnetic Pole, Geological Survey of Canada
  • Oulu Space Physics Textbook, University of Oulu
  • Tethers in Space, Marshall Space Flight Center, NASA
• Aurora
  • Aurora (Northern Lights), Time lapse movie of an aurora display on Sep/24/2006 in British Columbia, Canada
• magnetometer networks
  • Circum-pan Pacific Magnetometer Network (CPMN), Kyushu University [page encoded in Shift JIS]
  • Geophysical Institute Magnetometer Array (GIMA), University of Alaska
  • Greenland Chain, Danish Meteorological Institute
  • International Monitor for Auroral Geomagnetic Effects (IMAGE), Finnish Meteorological Institute
  • International Real-time Magnetic Observatory Network (Intermagnet)
  • Magnetometer Array for Cusp and Cleft Studies (MACCS), Augsburg College -- Boston University
  • Magnetometer Array on the Greenland Ice Cap (MAGIC), University of Michigan
  • Sub-Auroral Magnetometer Network (SAMNET), University of York
• space weather
  • Solar Terrestrial Activity Report, Jan Alvestad, DX-Listeners' Club
  • Space Environment Center (SEC), National Oceanic Atmospheric Administration (NOAA)
  • Space Weather: A Research Perspective, National Research Council
  • Space Weather Bureau
  • Space Weather Today, University Corporation for Atmospheric Research (UCAR)

---

prev | up | next

Another quality webpage by Glenn Elert

home | contact bent | chaos | eworld | facts | physics