Larry Sibik, age 12, of North Branch, Minnesota, for his question:
What exactly is the solar wind?
Our starry sun is big enough to engulf one and one third million earth sized planets. It contains 99.8 per cent of all the material in the Solar System and its seething core is 100 times denser than water. It is a raging nuclear furnace that converts four billion tons of matter into energy every second, day and night. Fortunately the planet earth is placed at a nice safe distance from these fierce outpourings of solar energy.
The so called solar wind is an outpouring of gaseous particles from the sun's seething surface. We speak of solar storms and solar winds, though they hardly are related to the breezy weather events that blow around in the earth's atmosphere. Our atmosphere works with enormous masses of dense air. In its lower levels, the concentration of gaseous molecules amounts to about one billion billion to the cubic centimeter. The solar wind, on the average, contains about five particles per cubic centimeter.
Nevertheless, exposure to an earthy gale may be safer than exposure to the solar wind. There are two main reasons why. The solar wind is made of electrically charged particles and they travel at fast, penetrating speeds. The solar wind slows down somewhat as it gets farther from the sun, but even at a distance of 93 million miles it whizzes past the earth at an average speed of about 300 miles per second.
The sun's nuclear energy surges continuously outward in all directions. It is estimated that this never ceasing output equals about 390 sextillion kilowatts, which is 390 plus 21 zeros. About one two billionths of the total output reaches our upper atmosphere and almost half of this reaches the surface of the earth. In 40 minutes, our small helping of the total solar energy equals all the electrical power that modern mankind uses in a whole year.
These and other basic facts led scientists to suspect that the sun's outpouring energy must carry along streams of particles from the solar surface. This was proved in 1962, when the Mariner II space probe took measurements in and above our upper atmosphere. At that time, the particles streaming constantly from the sun were called the solar wind. And later evidence revealed that this so called solar wind streams on and on, throughout the solar system and possibly beyond.
Nobody was surprised to learn that in the earth's neighborhood the solar wind's average speed is somewhat faster than a million miles per hour. After all, its tiny particles are launched by the fantastic energies of the seething sun.
Nobody was surprised to learn that solar wind particles are electrically charged ions, mostly protons and electrons plus a few helium nuclei. Normal atoms naturally would be stripped to ions in the sun's heat. Fortunately, the planet Earth has a built in defense against this solar bombardment. It is a monster magnet, with magnet' power to deflect the speeding ions from the surface. Scientists suspect that at least some of them are trapped in the enormous magnetosphere that extends above the earth, far out into space.