The impact of space weather has been apparent in the polar skies for years. When the first human beings crossed the land bridge from Asia to the Western Hemisphere, above them danced the ghostly greens and yellows and reds of the northern aurora.
That dance of diaphanous color continues today, but its impact is more substantial. The black-out of the Hydro-Quebec electric power grid across eastern Canada. The disruption of most of the pager systems in the United States. The loss of a telecommunications satellite designed for world service. The web of modern life extends above the earth as well as across its surface, and increasingly depends on technologies that can be vulnerable to space weather. Below are listed some of the ways several technologies can be adversely affected.
As spacecraft components have become smaller, the miniaturized systems have become increasingly vulnerable to energetic solar particles. These particles can cause physical damage to microchips and can change software commands in onboard computers.
Intense concentrations of energetic particles can cause "deep charging" or "bulk charging" in satellites. This happens when the particles, chiefly electrons, penetrate the outer covering of a satellite and deposit their charge in its inner parts. When a sufficient charge accumulates in any one part, its tendency is to become neutral—by discharging to other components. The discharge can be destructive to the satellite’s electronic systems.
Another phenomenon is differential charging. During geomagnetic storms the number and energy of electrons and ions increase. When a satellite passes through such an energized environment, the charged particles striking the spacecraft cause different portions of it to be differentially charged. Eventually, electrical discharges can arc across the spacecraft’s components, harming and possibly disabling them.
Geomagnetic storms heat the upper atmosphere, causing it to expand. Other space weather phenomena, such as increased solar ultraviolet emissions, do the same. The heated air rises, significantly increasing the density of the sparse gas at that altitude—about 700 miles—where many satellites orbit. The result is increased drag, causing the satellites to slow. Unless such low-earth-orbit satellites are routinely boosted to higher orbits, they slowly fall, and eventually burn up.
Many communication systems make use of the ionosphere to send radio signals over long distances. Ionospheric storms, however, cause some radio frequencies to be absorbed while others are reflected, which results in rapidly fluctuating signals. TV and commercial radio stations are not much affected by these conditions, but ground-to-air, ship-to-shore, and amateur radio are frequently disrupted.
Some military detection or early-warning systems are also affected by space weather. Over-the-Horizon Radar bounces signals off the ionosphere in order to monitor the launch of aircraft and missiles from long distances. During geomagnetic storms, this technology can be severely hampered by radio clutter. Civilian agencies have similar concerns. The Federal Aviation Administration routinely receives alerts of solar radio bursts so that communication problems can be anticipated.
Navigation systems like LORAN and OMEGA are adversely affected when solar activity disrupts their signal propagation. The OMEGA system, for example, consists of eight transmitters located throughout the world. Airplanes and ships use the very low frequency signals from these transmitters to determine their positions. During solar events and geomagnetic storms, however, the system can give navigators information that is inaccurate by as much as several miles. If navigators are alerted that a proton event or geomagnetic storm is in progress, they can switch to other systems. GPS devices, however, also can be affected by the sudden variations in ionosphere density that solar activity—space weather—causes.
When magnetic fields fluctuate or move in the vicinity of a conductor such as a wire, an electric current is induced in the conductor. This happens on a gigantic scale during geomagnetic storms. Power companies transmit alternating current to their customers via long transmission lines. The nearly direct currents induced in these lines from geomagnetic storms can cause overloads, transformer burn outs, and other damage.
Rapidly fluctuating geomagnetic fields can induce currents in pipelines—which can cause flow meters in the pipelines to transmit incorrect information. The phenomenon also dramatically increases the rate of corrosion in the pipeline. If engineers unwittingly attempt to balance the current during a geomagnetic storm, corrosion rates may increase even more.
Earth’s magnetic field is used by geologists to determine subterranean rock structures. For the most part, they are searching for oil, gas, or mineral deposits. But the true magnetic signatures of such features can be detected only when the earth’s field is quiescent.
Intense solar flares release very-high-energy particles that can be as injurious to people as low-energy radiation from nuclear blasts. Earth’s atmosphere and magnetosphere provide adequate protection for people on the ground, but astronauts in space are subject to potentially lethal dosages of radiation. The penetration of high-energy particles into living cells leads to chromosome damage and, potentially, cancer. Large doses can be fatal immediately.
Solar protons with energies greater than 30 million-electron volts are particularly hazardous. In October 1989, the sun produced enough energetic particles that an astronaut on the moon, wearing only a space suit and caught out in the brunt of the storm, would probably have died.