Anomaly in Earth's magnetic field

Help

Nasa scientist Dr Jack Connerney has been studying the growth of a weak patch in Earth's magnetic field, known as the South Atlantic Anomaly, thought to be linked to flow patterns in the planet's molten outer-core.

The magnetic field falls to below 30 microteslas (0.3 gauss), half the strength of that toward the poles, resulting in problems for satellites passing over the region.

Horizon: The Core is on BBC Two at 21:00 BST on Wednesday 31 August. Watch more clips or catch up afterwards via iPlayer.

Copyright © 2015 BBC. The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.