Anyone watching a compass needle point steadily north
might suppose that Earth’s magnetic field is a constant. It’s not.
Researchers have long known that certain expected changes are afoot.
The north magnetic pole routinely moves, as much as 40
km/yr, causing compass needles to drift over time. Moreover, the global
magnetic field has weakened 10% since the 19th century.
A new study
by the European Space Agency’s constellation of Swarm satellites
reveals that changes may be happening even faster than previously
thought. In this map, blue depicts where Earth’s magnetic field is weak
and red shows regions where it is strong:
Data from Swarm, combined with
observations from the CHAMP and Ørsted satellites, show clearly that
the field has weakened by about 3.5% at high latitudes over North
America, while it has strengthened about 2% over Asia. The region where
the field is at its weakest – the South Atlantic Anomaly – has moved
steadily westward and weakened further by about 2%. These changes have
occured over the relatively brief period between 1999 and mid-2016.
Earth’s magnetic field protects us from solar storms and
cosmic rays. Less magnetism means more radiation can penetrate our
planet’s atmosphere. Indeed, high altitude balloons launched by
Spaceweather.com routinely detect increasing levels of cosmic rays over California. Perhaps the ebbing magnetic field over North America contributes to that trend.
Swarm is a trio of satellites equipped with vector magnetometers capable of sensing Earth’s magnetic field all the way from orbital altitudes down to the edge of our planet’s core. The constellation is expected to continue operations at least until 2017, and possibly beyond, so stay tuned for updates. Cr Spaceweather
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