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The Magnetosphere
In reality, the action of the solar wind changes this picture rather dramatically. The axis of the field is tilted by about 11 degrees to the axis of rotation of the Earth. No one knows why, but these kinds of tilts are found among the magnetic fields of some of the other planets, too.
On the daytime side, the field is pushed in by the solar wind pressure, and on the nighttime side, it is invisibly stretched out like a comet's tail. Scientists call the region near the Earth where its field controls the motions of electrically charged particles the magnetosphere. As the Earth rotates, and as the solar wind and coronal mass ejections buffet it from the outside, the magnetosphere trembles and can become stormy. When these rapid, though subtle, changes happen, compass bearings can become unreliable by up to several degrees at the Earth's surface. In space, even more dramatic changes can happen.
When the solar wind and the magnetosphere are taken together as a system, they operate
like a set of powerful, but invisible, valves that open and close depending on their
polarity. When the solar wind's magnetic field is of the south-
Changes in the solar wind and in the magnetosphere can also cause the magnetotail region to change in complex ways. The magnetotail resembles a comet's tail and is stretched by the solar wind into a vast cylinder of magnetism nearly one million kilometers long. Magnetic fields in the magnetotail can snap like rubber bands and reconnect themselves, but this time the particles flow down these field lines and plunge deep into the interior of the magnetosphere cavity.
Some of these particles can take up temporary residence in an equatorial zone called
the ring current. In this vast, invisible river nearly 40,000 kilometers wide, positively-
Source:NASA
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Every square foot of the Earth is pierced by a line of magnetic force, which loops from deep inside the Earth, and far into space, only to return back in a great closed circuit thousands of miles away. If there were no Sun or solar wind, the Earth's magnetic field would extend far beyond the orbit of the moon and millions of kilometers into interplanetary space, in the same shape as a bar magnet field outlined by iron filings.