South Magnetic Pole

Locations of South Magnetic Pole from direct observation and model prediction.[1]

The South Magnetic Pole is the wandering point on the Earth's Southern Hemisphere where the geomagnetic field lines are directed vertically upwards. It should not be confused with the South Geomagnetic Pole described later.

For historical reasons, the "end" of a freely hanging magnet that points (roughly) north is itself called the "north pole" of the magnet, and the other end, pointing south, is called the magnet's "south pole". Because opposite poles attract, the Earth's South Magnetic Pole is physically actually a magnetic north pole (see also North Magnetic Pole § Polarity).

The South Magnetic Pole is constantly shifting due to changes in the Earth's magnetic field. As of 2005 it was calculated to lie at 64°31′48″S 137°51′36″E / 64.53000°S 137.86000°E / -64.53000; 137.86000,[2] placing it off the coast of Antarctica, between Adelie Land and Wilkes Land. In 2015 it lay at 64°17′S 136°35′E / 64.28°S 136.59°E / -64.28; 136.59 (est).[3] That point lies outside the Antarctic Circle. Due to polar drift, the pole is moving northwest by about 10 to 15 kilometers per year. Its current distance from the actual Geographic South Pole is approximately 2860 km.[1] The nearest permanent science station is Dumont d'Urville Station. Wilkes Land contains a large gravitational mass concentration.

North Magnetic Pole[4](2001) 81°18′N 160°04′W / 81.3°N 160.06°W / 81.3; -160.06(2004 est) 82°18′N 113°24′W / 82.3°N 113.4°W / 82.3; -113.4 (2007) 83°57′N 120°43′W / 83.95°N 120.72°W / 83.95; -120.72 (2015) 86°17′N 160°04′W / 86.29°N 160.06°W / 86.29; -160.06[3][5]
South Magnetic Pole(1998) 64°36′S 138°30′E / 64.6°S 138.5°E / -64.6; 138.5(2004 est) 63°30′S 138°00′E / 63.5°S 138.0°E / -63.5; 138.0 (2007) 64°29′49″S 137°41′02″E / 64.497°S 137.684°E / -64.497; 137.684[6] (2015) 64°17′S 136°35′E / 64.28°S 136.59°E / -64.28; 136.59[3]

Expeditions

Early unsuccessful attempts to reach the magnetic south pole included those of French explorer Dumont d'Urville (1837–40), American Charles Wilkes (expedition of 1838–42) and Briton James Clark Ross (expedition of 1839 to 1843).[7]

The first calculation of the magnetic inclination to locate the magnetic South Pole was made on January 23, 1838 by the hydrographer Clément Adrien Vincendon-Dumoulin, a member of the Dumont d'Urville expedition in Antarctica and Oceania on the corvettes "L'Astrolabe" and "Zélée" in 1837-1840, which discovered Adelie Land.

On 16 January 1909 three men (Douglas Mawson, Edgeworth David, and Alistair Mackay) from Sir Ernest Shackleton's Nimrod Expedition claimed to have found the South Magnetic Pole,[8] which was at that time located on land. However, there is now some doubt as to whether their location was correct.[9] The approximate position of the pole on 16 January 1909 was 72°15′S 155°09′E / 72.25°S 155.15°E / -72.25; 155.15.[10]

Fits to global data sets

The South Magnetic Pole has also been estimated by fits to global sets of data such as the World Magnetic Model (WMM) and the International Geomagnetic Reference Model (IGRF).[1] For earlier years back to about 1600, the model GUFM1 is used, based on a compilation of data from ship logs.[11]

South Geomagnetic Pole

The Earth's geomagnetic field can be approximated by a tilted dipole (like a bar magnet) placed at the center of the Earth. The South Geomagnetic Pole is the point where the axis of this best-fitting tilted dipole intersects the Earth's surface in the southern hemisphere. As of 2005 it was calculated to be located at 79°44′S 108°13′E / 79.74°S 108.22°E / -79.74; 108.22,[12] near the Vostok Station. Because the field is not an exact dipole, the South Geomagnetic Pole does not coincide with the South Magnetic Pole. Furthermore, the South Geomagnetic Pole is wandering for the same reason its northern magnetic counterpart wanders.

See also

References

  1. 1 2 3 NOAA National Geophysical Data Center. "Wandering of the Geomagnetic Poles". Retrieved October 10, 2011.
  2. ↑ "Geomagnetism Frequently Asked Questions". NGDC. Retrieved 11 January 2009.
  3. 1 2 3 British Geological Survey - Magnetic Poles
  4. ↑ "Geomagnetism, North Magnetic Pole". Geological Survey of Canada. Natural Resources Canada. Archived from the original on 26 March 2010. Retrieved 11 January 2009.
  5. ↑ World Data Center for Geomagnetism, Kyoto. "Magnetic North, Geomagnetic and Magnetic Poles". Retrieved 2012-07-03.
  6. ↑ "Poles and Directions". Australian Antarctic Division. 2011. Retrieved October 11, 2011.
  7. ↑ Antarctic Treaty System: an Assessment, p. 90, US National Research Council, 1986
  8. ↑ "FAQs from primary schools - British Antarctic Survey". Antarctica.ac.uk. 2011-03-11. Retrieved 2012-11-09.
  9. ↑ "The Magnetic South Pole". Ocean Bottom Magnetology Laboratory. Woods Hole Oceanographic Institute. Retrieved October 11, 2011.
  10. ↑ Shackleton, Roland Huntford
  11. ↑ Jackson, Andrew; Jonkers, Art R. T.; Walker, Matthew R. (2000). "Four centuries of geomagnetic secular variation from historical records". Philosophical Transactions of the Royal Society A. 358 (1768): 957–990. doi:10.1098/rsta.2000.0569.
  12. ↑ "Geomagnetism Frequently Asked Questions". Ngdc.noaa.gov. Retrieved 2012-11-09.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.