The Solar Wind

Over the course of the year, northerners receive less sunlight than those farther south, but, in one sense, they make up for it by getting more of the direct effects of the solar wind. Like sunlight, the solar wind derives from the sun, but it has quite different characteristics. Sunlight is composed of electromagnetic waves whereas the solar wind is made up of tiny particles, mostly electrons and protons.

Sunlight travels to the earth in only about eight minutes, but it takes a day or two for the particles in the solar wind to make the trip. Even so, the solar wind moves right along, traveling at 300,000 to more than 500,000 kilometers per second, fast enough to make the trip to earth in a day or two. Despite the high wind speed, a person exposed to it would be incapable of sensing the solar wind directly because of the low density in the wind. However, the particles in the solar wind travel so fast that they would mortally damage a person's exposed body in a short time.

The bulk of the particles in the solar wind are the basic building blocks of matter, electrons and protons They continuously boil off the sun's surface and speed outward in all directions, to distances well beyond the earth. Compared to the number of air molecules at the earth's surface, the number of particles in a unit volume of the solar wind is tiny, in fact, less than a billion billion times less. The density of particles in the wind is only about one per cubic centimeter, a density considered on earth to be an excellent vacuum.

Even though the solar wind has so few particles per unit volume, the wind has a profound effect upon the earth, especially at high latitudes. The earth's magnetic field interacts with the particles in the solar wind to deflect them away from the equatorial region. But at higher latitudes, they do move down into the high atmosphere. When they impact the atmospheric gases there they heat up the gases and also create the visible aurora and electrical currents in the high atmosphere. These currents, in turn, induce other currents in the earth and in long pipelines and power transmission systems. Current in the pipelines increases their rate of corrosion, and the current in the transmission lines trips breakers to cause power outages.

Extra strong blasts of solar wind emanate from sunspots. When these more intense blasts arrive at earth, auroras tend to be bright and widespread, and there are disturbances to radio communications and to the direction a compass needle points.

It is conjectured, but not proven, that variations in the solar wind may affect the earth's global weather. Evidence is mounting that past solar wind variations have influenced the climate, so it seems likely that an effect on weather will someday be found.