Dependence of the duration of geomagnetic polarity reversals on site latitude.

摘要: An important constraint on the processes governing geodynamo—the flow in outer core responsible for generating Earth's magnetic field—is duration of geomagnetic polarity reversals; that is, how long it takes field to reverse1. It is generally accepted strength drops low levels during reversals, and direction progresses through a 180° change while weak1. The time this process happen, however, remains uncertain, with estimates ranging from few thousand up 28,000 years. Here I present an analysis available sediment records four most recent reversals. These yield average estimate about 7,000 years directional occur. variation mean not random, but instead varies site latitude, shorter durations observed at low-latitude sites, longer mid- high-latitude sites. Such latitude predicted by simple geometrical reversal models, which non-dipole fields are allowed persist axial dipole decays zero then builds opposite direction, provides numerical dynamo models.