What is Magnetic Field ?

Titan, which orbits Saturn, is the only moon with a dense atmosphere. Its lakes and seas are made of methane and ethane. This unusual moon also has large, windswept dunes that are hundreds of miles long, over a mile wide, and hundreds of yards high.

For example, in 1819, Danish physicist and chemist Hans Christian Orsted discovered that an electric current creates a magnetic field around it.

At first, the existence of dunes didn’t make sense because we thought Titan only experienced light breezes over its surface. But later research suggested that winds must be stronger than previously believed. NASA’s spacecraft Cassini also sent pictures of the particles that created these dunes.

Magnetic field, a vector field in the neighbourhood of a magnet, electric current, or changing electric field, in which magnetic forces are observable.

In 1825, André-Marie Ampère proposed a model of magnetism where this force was due to perpetually flowing loops of current, instead of the dipoles of magnetic charge.

“It was surprising that Titan had particles the size of grains of sand—we still don’t understand their source—and that it had winds strong enough to move them,” said Devon Burr of the University of Tennessee. “Before seeing the images, we thought that the winds were likely too light to accomplish this movement.”

Magnetic fields such as that of Earth cause magnetic compass needles and other permanent magnets to line up in the direction of the field.

In 1831, English scientist Michael Faraday showed that a changing magnetic field generates an encircling electric field. In effect, he discovered electromagnetic induction, which was characterized by Faraday’s law of induction (aka. Faraday’s Law).

But scientists were most puzzled by the shape of the dunes. According to data provided by Cassini, the winds usually blew east to west. But the dunes around craters and mountains looked like they’d been created by winds blowing in the other direction.

Between 1861 and 1865, Scottish scientist James Clerk Maxwell published his theories on electricity and magnetism – known as the Maxwell’s Equations.

In a NASA high-pressure wind tunnel, Burr and her team spent six years recreating the conditions of wind and sand on Titan. Finally, they found that the wind had to blow at least 50 percent faster than originally believed to create the dunes. Titan’s dense atmosphere made the faster speeds necessary.

Magnetic fields force moving electrically charged particles in a circular or helical path. This force—exerted on electric currents in wires in a magnetic field—underlies the operation of electric motors.

Between 1861 and 1865, Scottish scientist James Clerk Maxwell published his theories on electricity and magnetism – known as the Maxwell’s Equations.

In a NASA high-pressure wind tunnel, Burr and her team spent six years recreating the conditions of wind and sand on Titan. Finally, they found that the wind had to blow at least 50 percent faster than originally believed to create the dunes. Titan’s dense atmosphere made the faster speeds necessary.

Around a permanent magnet or a wire carrying a steady electric current in one direction, the magnetic field is stationary and referred to as a magnetostatic field

These equations not only pointed to the interrelationship between electricity and magnetism, but showed how light itself is an electromagnetic wave.

Their discovery also explained the shape of the dunes. According to their model, the winds on Titan are usually light, blowing east to west, and are therefore unable to create dunes. But twice every Saturn year, which is equivalent to 30 Earth years, the wind blows faster in the other direction when the Sun crosses Titan’s equator. Burr believes those quick shifts in wind are when the dunes are created, and that accounts for their shape. Cassini may have missed these high wind speeds because they don’t happen often.

At any given point its magnitude and direction remain the same. Around an alternating current or a fluctuating direct current, the magnetic field is continuously changing its magnitude and direction.

Another NASA spacecraft, MESSENGER, has provided new insights into Mercury’s early planetary history. Originally, scientists believed that Mercury never had active volcanoes because it lacked the volatile compounds in its interior that create the explosions. But pictures from MESSENGER had researchers scrambling to rework their theories.

A classic example of a magnetic field is the field created by an iron magnet.

MESSENGER’s photos showed the presence of pyroclastic ash deposits, which are made from fragments of rock blasted from the vents of volcanoes. So Mercury obviously had volatile compounds. But the data also showed that volcanoes erupted for much of Mercury’s history.

Magnetic fields may be represented by continuous lines of force or magnetic flux that emerge from north-seeking magnetic poles and enter south-seeking magnetic poles.

As previously mentioned, the magnetic field can be illustrated by surrounding it with iron filings, which will be attracted to its field lines and form in a looping formation around the poles.

A research team from Brown University believes the eruptions happened over an extended time frame. They came to that conclusion by looking at the vents of the volcanoes. If the volcanoes had all exploded around the same time, then all the vents would be degraded by about the same amount. But the scientists observed different amounts of degradation, which is consistent with volcanic eruptions over a much longer period of time.

The density of the lines indicates the magnitude of the magnetic field. At the poles of a magnet, for example, where the magnetic field is strong, the field lines are crowded together, or more dense.