All permanent magnets will loose its strength and demagnetization will occur after a period of time. Then what about our earth’s magnetic field which is very much similar to that of a bar magnet?!
Well, the earth’s magnetic field also “changes”, but in a different manner.
WHY DO WE BOTHER ABOUT EARTH’S MAGNETIC FIELD!?
The Sun, which is a gas cloud of magnetized materials and plasma, ejects its materials in the form of solar flares. These solar winds pass through the earth at supersonic speed. And it includes cosmic radiations and high energy particles. When exposed to these high energy particles, our DNA can get damaged, causing cancer. But we are lucky as our earth protects us from these cosmic radiations using the magnetic field as a shield. Earth’s magnetic field interacts with these charged particles and trap them within its regions. These trapped particles remain in space in a belt like region which is known as the Van Allen belt. That is, earth protects us from the deadly cosmic radiations coming from space, using its magnetic field, unlike other planets in the solar system.
HOW EARTH’S MAGNETIC FIELD IS FORMED?
If we think about a commonly used bar magnet (of a magnetic material), its magnetic field is formed when the small fields of its constituent particles get aligned in a particular way. But earth’s magnetic field cannot be formed in this manner, but in a more complex manner. When looked at the structure, the interior of the earth, the core (about 3000 km below the surface, that is, below the solid crust and mantle), is mainly made up of iron. The outer core is in the form of liquid and the inner core is solid iron. As the earth rotates, the inner regions also rotate, at a rate faster than the outer regions. That means the liquid metals in the outer core are constantly moving, not in a specific pattern but in a very messy way. These movements create electrical currents which in turn generate a continuously changing electromagnetic field.
The magnetic field of earth, formed in this manner, having north and south magnetic poles (dipole field) is not very static. Note that the earth’s magnetic poles are not aligned with its rotation axis. In an “earth’s timescale” (over thousands of years), this field changes its strength and direction. We have evidences of these changes from the study of fossils. And studies show that the direction of the field can even flip over thousands of years.
Recently, analyzing the satellite data, scientists have found that the earth’s magnetic north pole is moving northwards, that is, towards Siberia, at a speed of about 60 km per year, from its initial position over the boundary of Canada, precisely located for the first time back in the 1800s. And this movement is accelerating as the years are passing. Also, the field has lost around 9% of its strength on a global average, over the last 200 years. Past records indicate that the decrease in the field strength may be an indication of the triggering of the reversal/flipping of the magnetic poles. Does that mean the polarity of the earth’s magnetic field is about to reverse? Well, some people believe, the acceleration of the movement of the north pole maybe an indication that we are at an early stage of reversal. And we don’t know exactly when this reversal may happen. But it will happen for sure. And it is due to the little ‘complicated’ motion of the earth’s outer core.
What happens to us, when such changes occur in the magnetic field? Do we get exposed to more cosmic rays? Or whether life gets extinct?
We are not very sure about the changes that may happen to the life on earth, but there aren’t any evidence of a catastrophic event happened in the past. There are animals relying on the earth’s magnetic field for navigation and they surely will get affected due to any change in the field. Also the amount of cosmic radiations entering earth’s atmosphere may increase if the field strength decreases or changes its direction, but that may not be in a huge amount. We tend to believe that these changes are part of the evolution.
References: nature
Read this article about the aurora in Mars- Green-glowing Oxygen Detected on Mars
Author
