The magnetic field that surrounds our planet is constantly changing. But recently, near the Arctic, it has been so active that researchers had to release a crucial update to a computer model that allows maps and other navigation software to correctly point north. The public release of this update to the World Magnetic Model (WMM) has been highly anticipated, but was delayed until Monday due to the recent US government shutdown.
Unlike the geographic North Pole, which stands at the top of the globe, the magnetic North Pole moves, and historically it does so at a fairly constant rate. Lately, it is moving at about 31 miles (50 kilometers) per year. Since compasses were invented hundreds of years ago, we have used the magnetic field to navigate with compasses that generally point north. But as the magnetic North Pole moves further away from the geographic North Pole, figuring out where it is in the world can become much more difficult.
"The pole moved maybe around 1,000 kilometers [621 miles] between 1900 and 1990, and it also moved about 1,000 kilometers between the late 1990s and today, so it really sped up," says William Brown, a global geomagnetic field modeler for the British. Geological Survey, which worked on this update of the World Magnetic Model.
Cartographers found they needed to take into account the distance between geographic and magnetic North a long time ago, which you might notice if you look closely at paper maps. "If you go hiking and use a very old map, the correction you set the compass to will be written on the map somewhere, and that actually has an expiration date," says Brown.
When the pole moves, printed maps need to be reprinted, and digital maps used on smartphones and mapping software used by military and government agencies need to be updated. Every now and then it changes enough that airport runways get new names so that pilots, who sometimes use magnetic fields to navigate, know where to land.
For both digital and analog upgrades, that's where the WMM comes in. It is jointly funded by military mapping agencies in both the United States and the United Kingdom. It is generally updated every five years. Predict how much the pole will move and how much other parts of the magnetic field will move during that time frame.
"The magnetic field near the North Pole is changing even more than usual"
But in recent years, something strange happened: the magnetic field near the North Pole began to change even more than usual.
"The bug grew a little faster than normal, especially in the Arctic region far north near the Magnetic North Pole," says Arnaud Chulliat, a research scientist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration (NOAA). Who worked on the update. The first phenomenon was the moving North Pole, which is moving towards Siberia. That alone would not have been enough to get rid of the model. But the catalysts, in this case, were relatively sudden changes in the speed of the movement of molten iron in the Earth's core.
“Sometimes it speeds up, and sometimes it slows down. "The reason for the rapid pole shift is that the flow has accelerated in certain areas," says Brown. These changes in velocity are called geomagnetic pulses and are usually not as noticeable.
"Normally, it is a subtle event that has no practical impact," says Chulliat. "But here, in the current situation, this geomagnetic pulse combined with the fast-moving magnetic North Pole caused the error to increase faster than normal."
The effects of the wrong model are too small to be noticed in people's everyday lives, unless your everyday life involves using your smartphone compass in the immediate vicinity of the North Pole, but it got to the point where the model in the Arctic it just wasn't accurate enough for the researchers' comfort.
“I don't want to exaggerate the consequences of this. At lower latitudes, the current model is fine, "says Chulliat. "Only the area around the Magnetic North Pole is where the error will become substantial."
In 2017, WMM scientists decided it would be better to do another small update earlier this year rather than wait until the current model expired at the end of 2019.
Monitoring how the magnetic field moves can give researchers like Brown an idea of what is happening in the Earth's core some 1,800 miles below Earth's surface. But it also helps keep the model up to date. One reason Chulliat, Brown, and their colleagues were able to update the model before age five is that Earth's magnetic field is being monitored more closely today than ever. Three European satellites called Swarm measure the magnetic field every 90 minutes, and 160 research observatories constantly keep watch.
Data from all of these observatories were incorporated into the update. A calculator based on the model was released in January by the British Geological Survey, but the US launch of the same model was delayed until this week due to the government shutdown. (The World Magnetic Model is published online by NOAA, and the agency's websites were inaccessible until the US government reopened.)
Now the updated model is online and publicly accessible. It is expected to be accurate until the end of 2019, at which time the regularly scheduled update will be released, which will be valid from 2020 to 2025. Although this particular off-cycle update is unprecedented, the researchers say there is really no reason alarm.
"Don't panic," says Brown. “The magnetic field changes, and we've seen it change unexpectedly and quickly before. This is something we know. It is not something that we understand how it works, but we are aware that it happens ".
By Mary Beth Griggs
Original article (in English)