The Earth’s magnetic field has a giant weak spot roughly aligned with the south Atlantic, and 11 years of observations show it has grown dramatically in that time. The cause of the South Atlantic Anomaly (SAA) is still debated, but the changes show it is dynamic on a relatively short timescale, considering evidence it has persisted on geological timescales. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Without the Earth’s magnetic field , life would be unlikely here – at least, anything more complex than bacteria. The field shields the planet from bombardment by charged particles, and therefore helps maintain our atmosphere. So, it’s a little alarming that the gaps in our knowledge about it – including why it varies so much over th

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