The magnetosphere is the region that surrounds a planet and the magnetic field of that planet, in which charged particles are trapped and controlled by that planet’s magnetic field, rather than the solar magnetic field. More specifically, the Earth’s magnetosphere is the region of space where the Earth’s magnetic field is confined by the solar wind plasma, blowing outward from the Sun. The magnetosphere prevents most of the particles from the Sun, carried by solar wind, from hitting the Earth. This asymmetrical region surrounds Earth, extending from about one hundred to several thousand kilometers (about 36,000 miles) above the surface.

Because the Earth is made of magnetic elements such as Iron, Nickel, and Cobalt, the Earth acts as an extremely large magnet, which attracts these charged particles, among other things. In concurrence with that, as the Earth rotates, its hot core generates strong electric currents that produce the magnetic field, a.k.a. magnetosphere. The Sun and other planets have magnetospheres, but the Earth has the strongest one of all the rocky planets.

Like all magnets, the Earth also has both a North and South Pole. The Earth's north and south magnetic poles reverse at irregular intervals of hundreds of thousands of years. In addition, the poles wander over shorter periods of time (hundreds of years).

As the Sun’s corona continuously emits plasma (freely moving ions and electrons) into the solar system, the solar wind that carries it distorts the shape of the magnetosphere by compressing it at the front and causing a long tail to form on the side away from the Sun; this long tail is called the magnetotail.

Although the magnetosphere blocks most of the plasma, some particles from the solar wind can enter the magnetosphere. The particles that enter from the magnetotail travel toward the Earth and create an aurora. An aurora is a brilliant atmospheric phenomenon appearing as bands of light, sometimes visible in the night sky, in northern or southern regions of the Earth.

The picture above illustrates the magnetosphere and labels several of its key components.


Bow shock: a supersonic shock wave created when solar wind collides with another medium, such as a planet's magnetosphere; as seen in the diagram, it begins in front of the magnetosphere and forms around it in the same direction

Cusp: the point of intersection of two arcs; where the two sections of the magnetosphere meet

Lobes: the major region of the magnetotail, between the magnetopause and the neutral sheet; as seen in the diagram, the lobes have an opposite magnetic direction

Magnetopause: the outer boundary of the magnetosphere

Magnetosheath: the region of space between the bow shock and magnetopause, caused by solar wind; its particles are denser than those of the magnetosphere; also known as the heliosheath

Neutral Sheet: a sheet of plasma that extends down the magnetotail dividing the two lobes of the magnetosphere; also known as the plasma sheet

Trapping Region: the part of the magnetosphere that traps electrically charged particles (electrons, protons, and heavier atomic ions) or radiation; also known as radiation belt

The diagram above shows the magnetosphere and more of its components.


Aurora: a brilliant atmospheric phenomenon appearing as bands of light, sometimes visible in the night sky, in northern or southern regions of the Earth; caused by particles that pass through the magnetosphere

Corona: the outermost region of the Sun's atmosphere, which continually emits plasma into the solar system

Magnet: an object that is surrounded by a magnetic field and has the property of attracting iron or steel

Magnetotail: the long, trailing part of the magnetosphere on the side facing away from the sun; caused by solar wind, which compresses the front of the magnetosphere, which causes the tail to form on the opposite end

Plasma: an electrically neutral, highly ionized gas composed of freely moving ions and electrons; the fourth state of matter (other than solid, liquid, and gas); plasma is neutral because it is a mixture of negatively charged electrons and ions which are positively charged

Plasmasphere: a region inside the magnetosphere which captures plasma that flows from the ionosphere, so that there is a plasma build-up

Pole: an extremity of an axis through a sphere; in a magnet, one of two places where it is most intense; the two poles have opposite charges (+/-)

Solar Wind: a stream of high speed, ionized particles expelled from the Sun's corona

This picture shows the Sun's corona releasing solar wind, which collides with the Earth's magnetosphere and creates a bow shock.

These colorful skys are caused by auroras.

Various states of matter: (from the left) Plasma, Solid, Liquid, Gas, and Plasma

Top: Earth's atmosphere as it is now, WITH solar wind Bottom: Earth's atmosphere (if it was) WITHOUT solar wind



Earth's Magnetosphere