What is Magnetic Field ?

When the solar wind hits the ionosphere, the plasma piles up, which in turn creates a thin magnetosphere around the planet. A magnetosphere is an area around a planet where its magnetic field may repel solar wind.

But there are differences in the ways electrostatic and magnetic fields interact with the environment.

The arrangements of these filings will then correspond to the field lines, forming streaks that connect at the poles.

Venus Express can measure this weak magnetic field around Venus. But it suggested that there weren’t two holes behind Venus. Instead, scientists now believe that there are two wide, long cylinders that extend from the surface of Venus into outer space. It’s possible that charged particles are squeezed out of these cylinders like toothpaste from a tube.

Electrostatic flux is impeded or blocked by metallic objects. Magnetic flux passes through most metals with little or no effect, with certain exceptions, notably iron and nickel.

They also appear during polar auroras, in which visible streaks of light line up with the local direction of the Earth’s magnetic field.

But that raises another compelling mystery. What allows these magnetic fields to cut through the ionosphere, go down to the planet surface, and possibly even enter the planet? We may have shed light on one Venus mystery, but we ended up with another one.

The study of magnetic fields began in 1269 when French scholar Petrus Peregrinus de Maricourt mapped out the magnetic field of a spherical magnet using iron needles.

These two metals, and alloys and mixtures containing them, are known as ferromagnetic materials because they concentrate magnetic lines of flux. An electromagnet provides a good example.

Auroras, light shows in the sky more commonly known as the Northern or Southern Lights, usually form when the solar wind collides with the Earth’s magnetic field, also known as the magnetosphere. In other words, it’s a visible way that we see the Sun’s effect on Earth.

The places where these lines crossed he named “poles” (in reference to Earth’s poles), which he would go on to claim that all magnets possessed.

During the 16th century, English physicist and natural philosopher William Gilbert of Colchester replicated Peregrinus’ experiment. In 1600, he published his findings in a treaties (De Magnete) in which he stated that the Earth is a magnet. His work was intrinsic to establishing magnetism as a science.

Theta auroras may form at higher latitudes, closer to the poles, than typical auroras. The theta aurora can only be seen from above.

An air-core coil carrying direct current produces a magnetic field. If an iron core is substituted for the air core in a given coil, the intensity of the magnetic field is greatly increased in the immediate vicinity of the coil

In 1750, English clergyman and philosopher John Michell stated that magnetic poles attract and repel each other.

If the coil has many turns and carries a large current, and if the core material has exceptional ferromagnetic properties, the flux density near the ends of the core (the poles of the magnet) can be such that the electromagnet can be used to pick up and move cars.

The force with which they do this, he observed, is inversely proportional to the square of the distance, otherwise known as the inverse square law.

The formation of an aurora depends on the alignment between the interplanetary magnetic field that flows with the solar wind and the Earth’s magnetic field. When the two fields intersect, the Earth’s magnetic field will point north. But if the interplanetary field is pointing south, then the magnetic field lines will point in opposite directions. This causes a process called magnetic reconnection (that isn’t yet well-understood), which realigns the magnetic field lines in a new way

When charge carriers are accelerated (as opposed to moving at constant velocity), a fluctuating magnetic field is produced. This generates a fluctuating electric field, which in turn produces another varying magnetic field.

In 1785, French physicist Charles-Augustin de Coulomb experimentally verified Earths’ magnetic field.

The new alignment allows the solar wind particles to enter into the Earth’s magnetosphere, a huge magnetic bubble around our planet. When those solar particles flow along the planet’s magnetic field lines and collide with atoms in the Earth’s upper atmosphere, the aurora is born. In this case, the formation is most likely to take place 65–70 degrees north or south of the Earth’s equator.

This was followed by 19th century French mathematician and geometer Simeon Denis Poisson created the first model of the magnetic field, which he presented in 1824.

But theta auroras can happen at higher latitudes if the interplanetary magnetic field is pointing north instead of south. Scientists recently discovered that, when this happened, magnetic reconnection can trap plasma (which is ionized gas) inside the magnetosphere. The trapped plasma becomes hot, and this time, a theta aurora may be born.

By the 19th century, further revelations refined and challenged previously-held notions.

The result is a "leapfrog" effect, in which both fields can propagate over vast distances through space. Such a synergistic field is known as an electromagnetic field. This is the phenomenon that makes wireless communications and broadcasting possible.