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 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 approximately 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 < or = 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.
Tarduno
John A
JA
Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA. john@earth.rochester.edu
Cottrell
Rory D
RD
Watkeys
Michael K
MK
Hofmann
Axel
A
Doubrovine
Pavel V
PV
Mamajek
Eric E
EE
Liu
Dunji
D
Sibeck
David G
DG
Neukirch
Levi P
LP
Usui
Yoichi
Y