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

Abstract

Early Origin of Earth's Magnetic Field Earth's magnetic field protects us from stellar winds and radiation from the Sun. Understanding when, during the Earth's formation, the large-scale magnetic field was established is important because it impacts understanding of the young Earth's atmosphere and exosphere. By analyzing ancient silicate crystals, Tarduno et al. (p. 1238 ; see the Perspective by Jardine ) demonstrate that the Earth's magnetic field existed 3.4 to 3.45 billion years ago, pushing back the oldest record of geomagnetic field strength by 200 million years. This result combined with estimates of the conditions within the solar wind at that time implies that the size of the paleomagnetosphere was about half of that typical today, but with an auroral oval of about three times the area. The smaller magnetosphere and larger auroral oval would have promoted loss of volatiles and water from the early atmosphere.