Page 300 - NS-2 Textbook

ASTRONOMY 295

MAGNETOPAUSE

STABLE TRAPPING REGION

The magnetosphere is formed by the Sun's effect on Earth's magnetic field. The outermost boundary of the magnetosphere is the mag-
netopause. Notice the location of the Van Allen radiation belts.

Sunspots create electrical and electronic distmbances above or below the north and south poles. These rings
on Earth. The great hydrogen flares erupting from the are the nalTOW Starfish ring caused by a U.S. hydrogen
spots send x-rays and atomic particles racing thousands bomb exploded at a height of 250 miles in 1962; the hmer
of miles beyond the planets of am solar system. This bar- and outer Van Allen radiation belts; and the stable tmp-
rage is called the solar wind. This wind erodes the lunar ping region, which contains lower-energy particles. This
surface, creates comet tails, and even causes erratic last region extends almost the whole length of the mag-
changes in compass readings and the weather. It also af- netosphere. The magnetosphere, then, is the region over-
fects the height of the ionosphere, causing fading and lapping the exosphere, within which Earth's magnetic
static in shorhvave radio transmissions. field is confined by the solar wind.

THE MAGNETOSPHERE THE SUN'S ENERGY

The outermost layer of Earth's atmosphere is the exo- The Sun produces gigantic amounts of energy. It can
sphere, which extends to about 18,000 miles from the cause temperatures in excess of 100 degrees Fahrenheit at
planet's surface. Surrounding or overlapping the exo- a distal1ce of about 93 million miles-as we well know on
sphere is the 1!1agnetosphere. The magnetosphere is formed a hot summer's day. And consider this: Earth actually re-
by the Sun's effect on Earth's magnetic field. ceives less than one two-billionth of the Stm's energy. The
Earth acts as a huge magnet, surrotmded by a mag- rest is lost in space. The Sun's energy passes through
netic field. But this magnetic field does not dissipate into space by the process of radiation. It is this energy that
space. It is confined within the magnetosphere by the warms us, grows ow' crops, and gives us our seasons,
solar winds, which rush by at up to 900,000 miles per winds, and weather.
hour. The boundaly of the magnetosphere is called the The Sun actually is its own fuel. It literally is eating
maguetopause. It is 40,000 miles from Earth's surface on itself up at the rate of millions of tons of hydrogen each
the stmward side and is drawn out into a huge comet- second. But it contains enough hydrogen to keep going
like tail, between 3 and 4 million miles long, on the side for at least 5 billion more years. However, long before
away from the Sun. The magnetosphere changes its then-perhaps as soon as several hundred million years
shape daily as the strength of the solar wind varies. This from now-scientists speculate that the Stm will have
causes changes in the areas closer to Earth and affects burned up so much of its hydrogen fuel that it will
radio transmission and the 'weather. have to begin to expand to remain stable. Eventually, it
Inside the magnetosphere are huge numbers of will become a red giant star, with a radius about equal
charged particles that have been trapped by Earth's mag- to the radius of Earth's orbit. Thereaftel~ the Sun wiII
netic field. These particles circle Earth in four doughnut- shrink to ultimately become a white dwarf, with only
shaped regions, one artificial and three natural. Earth is the outer planets of our solar system surviving in orbit
in the doughnut hole, and there are no trapped particles around it.