Geodynamo, Solar Wind, and Magnetopause 3.4 to 3.45 Billion Years Ago

Stellar wind standoff by a planetary magnetic field prevents atmospheric erosion and water loss. Although the early Earth retained its water and atmosphere, and thus evolved as a habitable planet little is known about Earth's magnetic field strength during that time. We report paleointensity re...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2010-03, Vol.327 (5970), p.1238-1240
Main Authors: Tarduno, John A., Cottrell, Rory D., Watkeys, Michael K., Hofmann, Axel, Doubrovine, Pavel V., Mamajek, Eric E., Liu, Dunji, Sibeck, David G., Neukirch, Levi P., Usui, Yoichi
Format: Article
Language:English
Subjects:
Cooling
Crystals
Earth
Earth, ocean, space
Exact sciences and technology
External geophysics
Geological time
Geomagnetic fields
Geophysics
Magnetic fields
Magnetization
Magnetopause
Other topics in aeronomy and magnetospheric physics
Polar caps
Rotating generators
Solar physics
Solar wind
Sun
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Summary:Stellar wind standoff by a planetary magnetic field prevents atmospheric erosion and water loss. Although the early Earth retained its water and atmosphere, and thus evolved as a habitable planet little is known about Earth's magnetic field strength during that time. We report paleointensity results from single silicate crystals bearing magnetic inclusions that record a geodynamo 3.4 to 3.45 billion years ago. The measured field strength is ~50 to 70% that of the present-day field. When combined with a greater Paleoarchean solar wind pressure, the paleofield strength data suggest steady-state magnetopause standoff distances of ≤5 Earth radii, similar to values observed during recent coronal mass ejection events. The data also suggest lower-latitude aurora and increases in polar cap area, as well as heating, expansion, and volatile loss from the exosphere that would have affected long-term atmospheric composition.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1183445