Space Weather

Space weather is the concept of continuously changing environmental conditions in near-Earth space. It is different from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space. "Space weather" implicitly means the conditions in near-Earth space within the magnetosphere and ionosphere, but it is also studied in interplanetary (and occasionally interstellar) space.

The closest star, the Sun, looks serene at a distance of about 150 million kilometers away, but it is actually a seething nuclear cauldron that churns, boils, and often violently erupts. Parts of the Sun’s surface and atmosphere are constantly being blown into space, where they become the solar wind. Made up of hot charged particles, this wind streams out from the Sun and flows through the solar system, bumping and buffeting any objects it encounters. Traveling at more than a million kilometers per hour, the solar wind takes about three to four days to reach Earth. When it arrives at Earth the solar wind interacts with our planet’s magnetic field, generating millions of amps of electric current. It blows

Earth’s magnetic field into a tear-shaped region called the magnetosphere. Collectively, the eruptions from the Sun, the disturbances in the solar wind, and the stretching and twisting of Earth’s magnetosphere are referred to by the term space weather. Quite similar to terrestrial weather, space weather can also be calm and mild or completely wild and dangerous.

Adverse space weather conditions triggered by solar eruptions not only affect astronauts and spacecraft but also activities and equipment on Earth, including terrestrial power lines, communications, and navigation. For example, in space coronal mass ejections (CMEs) and solar flares can damage the sensitive electronic systems of satellites or trigger phantom commands in the computers responsible for operating various spacecraft. Even astronauts are at risk if they venture beyond the radiation-shielded portions of their space vehicles. On Earth space weather can interfere with radar. During a solar-induced magnetic storm electric currents can surge through Earth’s surface and sometimes disrupt terrestrial power lines. In 1989, for example, one such surge produced a cascade of broken circuits at Canada’s Hydro-Quebec electric power company, causing the entire grid to collapse in less than 90 seconds. All over Quebec the lights went out. Today an armada of satellites from the United States, Europe, Japan, and Russia help scientists around the world monitor and forecast space weather. Much of this effort has been focused through the International Solar Terrestrial Physics (ISTP) Program. Near solar maximum, more frequent episodes of “inclement” space weather are generally anticipated. Therefore, as the Sun approaches the maximum of its cycle, space weather forecasters and space scientists more closely monitor the space environment for signs of potentially stormy relationships between Earth and its parent star.

Questions to Ponder

• What is the temperature in space at present? What was the temperature 1 second after the Big Bang?
• What are the significant Space Weather characteristics considered while designing Space shuttles?