Earth's magnetosphere

On Earth we need a sensitive needle to detect magnetic forces. In space they are much, much weaker. These forces have a bigger role, around the Earth where they dominate the environment, a region known as the Earth's magnetosphere. This contains a mix of electrically charged particles, and electric and magnetic phenomena rather than gravity determine its structure. magnetosphere: fluctuations of the magnetic field known as magnetic storms and substorms, and the polar aurora or "northern lights," Satellites in space, however, sense much more: radiation belts, magnetic structures, fast streaming particles and processes which energize them.

 

What is magnetism?


 

The nature of magnetism force between electric currents: two parallel currents in the same direction attract, in oposite directions repel. In nature, magnetic fields are produced in the rarefied gas of space, in the glowing heat of sunspots and in the molten core of the Earth. Such magnetism must be produced by electric currents. The challenge is finding how those currents are produced.

 

Magnetic field lines


Compass needles outlining field lines

Field lines of the Earth start near the south pole of the Earth, curve around in space and converge again near the north pole. However, in the Earth's magnetosphere, currents also flow through space and modify this pattern: on the side facing the Sun, field lines are compressed earthward, while on the night side they are pulled out into a very long "tail," like that of a comet. Near Earth, however, the lines remain very close to the "dipole pattern" of a bar magnet, so named because of its two poles.Electrons and ions tend to stay attached to them. This attachment, they define an "easy direction" in the rarefied gas of space, a direction in which ions and electrons, as well as electric currents and certain radio-type waves, can easily move.


Electromagnetic Waves The space around a magnet is viewed as filled with field lines, but also developed an intuitive and perhaps mystical notion that such space was itself modified, even if it was a complete vacuum. Such a modified space is now known as an electromagnetic field. Today electromagnetic fields and other types of field as well are a cornerstone of physics. Their basic equations, suggested that they could undergo wave motion, spreading with the speed of light, and that this actually was light and that light was in fact an electromagnetic wave.


Nowadays a wide variety of such waves is known, from radio, very long waves, relatively low frequency to microwaves, infra-red, visible light, ultra-violet, x-rays and gamma rays,very short waves, extremely high frequency. Other such waves have been detected from the magnetospheres of distant planets, the Sun and the distant universe. X-rays, too, are observed to come from such sources and are the signatures of high-energy electrons there.



What Drives Earth's Magnetic Field?



 

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