Definition of Aurora

Aurora Borealis and Aurora Australis are glows that

are sometimes visible in the Northern and Southern Hemispheres,

respectively. They are informally known as the northern

lights and the southern lights. The glows are strongest

near the poles and originate in the Van Allen radiation belts,

which are regions where high-energy charged particles of the

solar wind that travel outward from the Sun are captured by

the Earth’s magnetic field. The outer Van Allen radiation belt

consists mainly of protons, whereas the inner Van Allen belt

consists mainly of electrons. At times, electrons spiral down

toward Earth near the poles along magnetic field lines and

collide with ions in the thermosphere, emitting light in the

process. Light in the aurora is emitted between a base level of

about 50–65 miles (80–105 km), and an upper level of about

125 miles (200 km) above the Earth’s surface.

The solar wind originates when violent collisions

between gases in the Sun emit electrons and protons, which

escape the gravitational pull of the Sun and travel through

space at about 250 miles per second (more than 1 million

km/hr) as a plasma known as the solar wind. When these

charged particles move close to Earth, they interact with the

magnetic field, deforming it in the process. The natural undisaurora

35

turbed state of the Earth’s magnetic field is broadly similar to

a bar magnet, with magnetic flux lines (of equal magnetic

intensity and direction) coming out of the south polar region

and returning back into the north magnetic pole. The solar

wind deforms this ideal state into a teardrop-shaped configuration

known as the magnetosphere. The magnetosphere has

a rounded compressed side facing the Sun, and a long tail

(magnetotail) on the opposite side that stretches past the

orbit of the moon. The magnetosphere shields the Earth from

many of the charged particles from the Sun by deflecting

them around the edge of the magnetosphere, causing them to

flow harmlessly into the outer solar system.

The Sun periodically experiences periods of high activity

when many solar flares and sunspots form. During these

periods the solar wind is emitted with increased intensity,

and the plasma is emitted with greater velocity, in greater

density, and with more energy than in its normal state. During

these periods of high solar activity the extra energy of

the solar wind distorts the magnetosphere and causes more

electrons to enter the Van Allen belts, causing increased

auroral activity.

When the electrons from the magnetosphere are injected

into the upper atmosphere, they collide with atoms and

molecules of gases there. The process involves the transfer of

energy from the high-energy particle from the magnetosphere

to the gas molecule from the atmosphere, which becomes

excited and temporarily jumps to a higher energy level. When

the gas molecule returns to its normal, regular energy level, it

releases radiation energy in the process. Some of this radiation

is in the visible spectrum, forming the Aurora Borealis in

the Northern Hemisphere and the Aurora Australis in the

Southern Hemisphere.

Auroras typically form waving sheets, streaks, and glows

of different colors in polar latitudes. The colors originate

because different gases in the atmosphere emit different characteristic

colors when excited by charged particles from the

magnetosphere, and the flickering and draperies are caused

by variations in the magnetic field and incoming charged particles.

The auroras often form rings around the magnetic

poles, being most intense where the magnetic field lines enter

and exit the Earth at 60–70° latitude.

Title Post:
Rating: 100% based on 99998 ratings. 99 user reviews.
Author:

Terimakasih sudah berkunjung di blog SELAPUTS, Jika ada kritik dan saran silahkan tinggalkan komentar