M is for Magnetosphere

I know, I know, I’m way behind on my A to Z posts. Life hit me hard this month but I’m doing my best to start catching up. I plan to post for two letters a day until I’m back on track. Thank you for reading :) 

A magnetosphere is the area of space near an astronomical object, like a planet, that contains it’s magnetic environment. This is where object’s magnetic field dominates and charged particles are controlled. Near the surface of the object, the magnetic field lines resemble those of a magnetic dipole. As you get father away from the object it’s magnetic field lines are greatly distorted by electric currents.

The Earth’s approximate dipole magnetic field is modified in interaction with the solar wind to create the magnetosphere By NASA [Public domain], via Wikimedia Commons

To give you an example, think of it as if the Earth is a huge dipole (2-pole) magnet. The magnetosphere extends several tens of thousands of kilometers into space and protects the Earth, and, by extension, us humans, from the charged particles of the solar wind, a stream of nasty plasma released from the upper atmosphere of the Sun. These winds and rays would strip away the upper atmosphere, including the ozone layer. The upper atmosphere is what protects us from harmful ultraviolet radiation.

The magnetosphere also protects us from harmful cosmic rays, high-energy charged particles that are mostly from outside the Solar system. For the most part though the Sun’s own magnetosphere, called heliosphere, protects us from those.

Sometimes the charged particles get inside the magnetosphere. They spiral around the field lines, bouncing back and forth between the poles several times per second. Some particles penetrate the ionosphere where the collide with the atoms there give rise to the aurorae, or northern lights.

Showing the variation between magnetic north (Nm) and “true” north (Ng). By JrPol (Own work) [GFDL or CC BY-SA 3.0], via Wikimedia Commons

Our magnetic field is quite strong due to the motion of the molten iron is the Earth’s core and our quick rotation rate in a process that is actually pretty complex. The magnet field is roughly aligned with the north and south poles, which is why we can find our way with a compass, but Earth’s magnetic field likes to wander about. Right now it is tilted at an angle of about 10 degrees. Every so often, about every several hundred thousand years or so, the magnetic field will actually reverse and the North and South Magnetic Poles will abruptly switch places.

Despite the name the magnetosphere is not shaped like a sphere. On the side of the Earth facing the sun the magnetosphere is compressed and pushed closer to Earth’s surface by the push of the solar winds from the sun. When the solar winds hit this side the slow abrupty, that particular area is called the magnetopause, or the bow shock.

On the night side the magnetosphere is stretched out and forms the magnetotail which extends far out into space. The magnetotail’s shape and length varies with the strength of the solar wind.

Schematic of magnetosphere. Original bitmap from NASA. SVG rendering by Aaron Kaase.This SVG image was created by Medium69.Cette image SVG a été créée par Medium69.Please credit this : William Crochot [Public domain], via Wikimedia Commons

The Sun’s magnetoshpere, also called the helioshphere, extends past all the planets and well into space. As mentioned before it protects our solar system from cosmic rays comic in from deep space. The sun’s magnetosphere is shaped much like our own and but the process that creates it is even more complex than the Earth’s.

Because the sun is not a solid it’s rotation is more like that of a fluid and some latitudes moving faster than others. This causes it’s magnetic field lines to become “wound up” like a rubber band. Eventually these bands “snap” causing solar flares which impact our own magnetosphere.

Jupiter also has a very large magnetosphere,  the largest of all the other planets in the Solar System. It’s magnetotail extends almost all the was to Saturn on it’s night side.

Magnetospheres are very important in astronomy and there is still a lot we don’t know about them. One thing we do know is that they are very  important for the formation of life on a planet. The Earth’s own magnetosphere is a highly dynamic and life here on Earth developed and is sustained under the protection of it. If it weren’t for the magnetosphere we would be here at all.


Image: Seen from the southern skies, the Large and Small Magellanic Clouds (the LMC and SMC, respectively) are bright patches in the sky. These two irregular dwarf galaxies, together with our Milky Way Galaxy, belong to the so-called Local Group of galaxies.

Astronomers once thought that the two Magellanic Clouds orbited the Milky Way, but recent research suggests this is not the case, and that they are in fact on their first pass by the Milky Way. The LMC, lying at a distance of 160 000 light-years, and its neighbour the SMC, some 200 000 light-years away, are among the largest distant objects we can observe with the unaided eye.

Both galaxies have notable bar features across their central discs, although the very strong tidal forces exerted by the Milky Way have distorted the galaxies considerably. The mutual gravitational pull of the three interacting galaxies has drawn out long streams of neutral hydrogen that interlink the three galaxies.

By ESO/S. Brunier (ESO) [CC BY 4.0], via Wikimedia Commons


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