For most of us, the Earth’s magnetic field may just be the source of convenient trekking and map reading.
But it has been proven long ago that navigation is the least significant utilization of this astronomical phenomenon. In fact, if it wasn’t for this magnetic field, there would not be any life on Earth. It protects the planet from getting fried up after every frequent solar storm. It does so by deflecting the incoming bombardment of electrically charged particles and radiation discharged by the sun.
This magnetic shield has been a source of study and debate ever since the 13th century. In the earliest study, it was considered that the cause of this magnetic field could be Polaris, the North star, or a huge magnetic island situated at the north pole. Though these studies may sound absurd now, they governed the astrophysics discipline until the year 1600. It is then a more logical, though not entirely rational, hypothesis was presented by William Gilbert. In his work ‘De Magnete’, he proposed the first ever publicized scientific column about magnetism, where he concluded that the Earth itself, like terella, is magnetic.
It was only in the year 1919, the most rational, yet not without paradoxes, solution for the Earth’s magnetic field was discovered, which was later named as Geodynamo. It is only this hypothesis that sounds compatible with all other astrophysics and geological phenomena, viz., pole reversion, the temperature conservation of Earth’s core, the oblate spheroid shape of the Earth, etc.
The Theory Of Geodynamo
The first clear rationalization of the concept of geodynamo was given by Walter M. Elsasser, the father of the present Dynamo theory. He stated that the magnetic field of Earth is the result of the electric currents that are induced in the outer core of the Earth, a 2000 km thick layer composed of mainly iron particles. The only possible source of this current can be the convention, one of the basic temperature related physics principles that demonstrates the collective movement of molecules within fluids when heated.
So, in simpler terms, the iron particles, in the fluid outer core of the planet, gets heated by the solid inner core, the temperature of which matches to that of sun’s surface. Then as it happens when we boil some liquid in a pan, the heated molten iron particles become less dense than the comparatively cooler ones and start moving upwards. When these particles reach further away from the source of heat, they cool down causing them to sink again nearer to the torrid inner core. This cycle repeats itself continually, and the iron particles in there create electric currents, which in turn develops the same magnanimous magnetic field that is protecting our planet of life.
The Great Paradox
Quite alike other theories of Earth’s magnetic field, the geodynamo, despite all its justifiable compilations, has its paradoxes. Strange as it may sound, this ‘classical model’ of Earth’s magnetic field is not quite plausible.
With the recent development in the field of knowledge about Earth’s temperature, it has become valid that for the geodynamo to work, the essential conditions are that the Earth had to be in a totally molten state with a burning core of 6800°C temperature, nearly four billion years ago. And it has to cool down slowly by almost 3000°C. But since researches proved that the temperature has cooled down only by 300°C, it is virtually impossible to establish the functionality of Geodynamo, as it is right now, without any other external factor.
Elimination of the Complexity
As discussed above, the paradox about geodynamo exists only when there are no external factors. Well, the good news is that a new perception is introduced recently, and this classical model can be used for further studies without any trace of doubt. The new perception includes the much-overlooked idea of the irregular orbital movements of the moon and that of Earth itself.
The possible effect of the moon has always been considered in this regards, but never exactly with this outlook. The idea is that the mantle of outer core of Earth deforms elastically due to the tidal effects caused by the irregular orbital movement of Earth and moon. The motion and unstable gravity can cause fluctuations, which in turn could stimulate the convection process of the liquid iron alloy in the mantle of the Earth, affecting the classical phenomenon of geodynamo.
This theory is even more plausible considering that the fulcrum of the moon’s rotational orbit is some distance below the outer surface of the Earth. Moreover, this hypothesis can also answer for those occasional heat pulses on Earth. So, perhaps, this long astrophysical debate about Earth’s magnetic field has at last reached its conclusion.
ABOUT THE AUTHOR
Alfonzo Nelson is an academic writer who has varied areas of interests that include Astrophysics, Botany, Literature, and History, on which he has published various posts.