Pinning Down the Sun-Climate Connection; Solar Influence Extends beyond Warm, Sunny Days

Beginning of article

Second in a two-part series on the sun-Earth connection

The solar flares that spew massive amounts of energy and particles earthward are notorious for the havoc they can wreak on satellites, power grids, and our planet's magnetic field (SN: 1/13/01, p. 26). The charged particles that slam into the outer fringes of the atmosphere also ionize the air and stimulate shimmering auroras. During periods of increased solar activity, particularly during high-points of the 11-year sunspot cycle, these breathtaking sky shows often appear far south of their normal Arctic venues.

Strong solar activity can also have substantial short-term influences; by cooling the atmosphere in some places and heating it in others. These meteorological effects typically last days or weeks. But many scientists propose that changes in the sun's magnetic field and radiation output during its 11-year cycle of activity also have longer-term effects. They influence the movement of weather systems and other aspects of atmospheric and climate patterns.

It's tough to discern the subtle climatic effects of solar variation amidst a cacophony of strong earthly influences--greenhouse gases, volcanoes, sulfate aerosols, to name a few. But using sophisticated statistical analyses of an ever-growing stockpile of climate and weather data, scientists say they're uncovering ways in which even small variations in solar activity could have big effects down at ground level.

Intense solar activity has substantial short-term effects that can shape Earth's weather. Consider the magnetosphere, which swaddles the planet at altitudes between 1,000 and 6,000 kilometers. It's composed of thick layers of charged particles--primarily protons and electrons--trapped in space by Earth's magnetic field. When a strong solar flare delivers a jolt to these belts, it can shake loose a torrent of these charged particles. Auroras, which at times of increased solar activity sprawl across the sky more often than average, are merely one result of this ionic rain upon the upper atmosphere.

An …