What happens if magnetic poles reverse

As a matter of geological record, the Earth's magnetic field has undergone numerous reversals of polarity. We can see this in the magnetic patterns found in volcanic rocks, especially those recovered from the ocean floors. In the last 10 million years, there have been, on average, 4 or 5 reversals per million years.

At other times in Earth's history, for example during the Cretaceous era, there have been much longer periods when no reversals occurred. Reversals are not predictable and are certainly not periodic in nature. Hence we can only speak about the average reversal interval.

Measurements have been made of the Earth's magnetic field more or less continuously since about Some measurements even go back to the s, for example at Greenwich in London.

If we look at the trend in the strength of the magnetic field over this time for example the so-called 'dipole moment' shown in the graph below we can see a downward trend. Indeed projecting this forward in time would suggest zero dipole moment in about years time.

This is one reason why some people believe the field may be in the early stages of a reversal. We also know from studies of the magnetisation of minerals in ancient clay pots that the Earth's magnetic field was approximately twice as strong in Roman times as it is now. Even so, the current strength of the magnetic field is not particularly low in terms of the range of values it has had over the last 50, years and it is nearly , years since the last reversal.

Also, bearing in mind what we said about 'excursions' above, and knowing what we do about the properties of mathematical models of the magnetic field, it is far from clear we can easily extrapolate to years hence. We have no complete record of the history of any reversal, so any claims we can make are mostly on the basis of mathematical models of the field behaviour and partly on limited evidence from rocks that retain an imprint of the ancient magnetic field present when they were formed.

For example, the mathematical simulations seem to suggest that a full reversal may take about one to several thousand years to complete.

This is fast by geological standards but slow on a human time scale. As above, we have limited evidence from geological measurements about the patterns of change in the magnetic field during a reversal. We might expect to see, based on models of the field run on supercomputers, a far more complicated field pattern at the Earth's surface, with perhaps more than one North and South pole at any given time.

We might also see the poles 'wandering' with time from their current positions towards and across the equator. The overall strength of the field, anywhere on the Earth, may be no more than a tenth of its strength now. Almost certainly not. The Earth's magnetic field is contained within a region of space, known as the magnetosphere, by the action of the solar wind.

The magnetosphere deflects many, but not all, of the high-energy particles that flow from the Sun in the solar wind and from other sources in the galaxy. By Karina Shah. This flip of the magnetic poles would have been devastating, creating extreme weather and possibly leading to the extinction of large mammals and the Neanderthals.

The magnetic poles wander and occasionally reverse around every , to , years, but we have little evidence on how this impacts our planet. Alan Cooper at the South Australian Museum in Adelaide and his colleagues have now provided some answers. What if one of those bands of extra radiation hits a very heavily populated part of the planet? Then, of course, there are the effects on all the creatures on the planet, as well as the effects on our electromagnetic system, the electric grid, and all the things we consider part of modern civilization.

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The phenomenon would have led to some dramatic and dazzling events. The weakening of the magnetic field meant that more space weather, such as solar flares and galactic cosmic rays, could head to Earth.

Perseverance rover has successfully landed on Mars and sent back its first images. Meanwhile, the ionized air would've increased the frequency of electrical storms -- something that scientists think caused humans to seek shelter in caves.

An upcoming reversal.