Soal Latihan dan Jawaban Reading Comprehension 39
The spectacular aurora light displays that appear in Earth’s atmosphere around the
north and south magnetic poles were once mysterious phenomena. Now, scientists have
data from satellites and ground-based observations from which we know that the
aurora brilliance is an immense electrical discharge similar to that occurring in a
(5) neon sign.
To understand the cause of auroras, first picture the Earth enclosed by its
magnetosphere, a huge region created by the Earth’s magnetic field. Outside the
magnetosphere, blasting toward the earth is the solar wind, a swiftly moving plasma of
ionized gases with its own magnetic filed. Charged particles in this solar wind speed
(10) earthward along the solar wind’s magnetic lines of force with a spiraling motion. The
Earth’s magnetosphere is a barrier to the solar winds, and forces the charged particles of
the solar wind to flow around the magnetosphere itself. But in the polar regions, the
magnetic lines of force of the Earth and of the solar wind bunch together. Here many of the
solar wind’s charged particles break through the magnetosphere and enter Earth’s
(15) magnetic field. They then spiral back and forth between the Earth’s magnetic poles
very rapidly. In the polar regions, electrons from the solar wind ionize and excite the
atoms and molecules of the upper atmosphere, causing them to emit aurora radiations
of visible light.
The colors of an aurora depend on the atoms emitting them. The dominant greenish
(20) white light comes from low energy excitation of oxygen atoms. During huge magnetic
storms oxygen atoms also undergo high energy excitation and emit a crimson light.
Excited nitrogen atoms contribute bands of color varying from blue to violet.
Viewed from outer space, auroras can be seen as dimly glowing belts wrapped
around each of the Earth’s magnetic poles. Each aurora hangs like a curtain of light
(25) stretching over the polar regions and into the higher latitudes. When the solar flares
that result in magnetic storms and aurora activity are very intense, aurora displays
may extend as far as the southern regions of the United States.
Studies of auroras have given physicists new information about the behavior of
plasmas, which has helped to explain the nature of outer space and is being applied in
(30) attempts to harness energy from the fusion of atoms.
Reading Comprehension 39
The factors that cause the variety of colors in auroras
The methods used to observe auroras from outer space
The formation and appearance of auroras around the Earth's poles
The periodic variation in the display of auroras
it increases the speed of particles from the solar wind
it is strongest in the polar regions
its position makes it difficult to be observed from Earth
it prevents particles from the solar wind from easily entering Earth's atmosphere
atoms and molecules
magnetic storms do not affect Earth
the speed of the solar wind is reduced
the excitation of atoms is low
solar flares are very intense
Before advances in technology, including satellites, scientists knew little about auroras.
New knowledge about the fusion of atoms allowed scientists to learn more about auroras.
Scientists cannot explain the cause of the different colors in auroras.
Until scientists learn more about plasma physics, little knowledge about auroras will be available.
"electrons" (line 16)
"ionize" (line 16)
"magnetosphere" (line 7)
"fusion" (line 30)