Chinese space scientists, working with American and European counterparts, have revealed the origin of the brilliant auroras -- often referred to as "northern lights", "southern lights" or "aurora borealis" -- seen at night.
Cao Jinbin, a researcher with the Center for Space and Applied Research under the Chinese Academy of Sciences, who was closely involved in the research, said that previously people believed auroras were caused by solar winds.
Using data collected from four satellites, scientists were able to overturn this view.
"We have found that auroras caused by solar winds are very weak and can scarcely be seen with the naked eye. The splendid and colorful auroras we see are actually caused by magnetic substorms, " Cao said.
By studying the data collected by European Space Agency (ESA) cluster satellites, scientists found that high-speed flows of electrified gas, known as bursty bulk flows (BBFs), are generated by magnetic substorms.
Auroras are caused mostly by energetic BBFs spiraling down Earth's magnetic field lines and colliding with atmospheric atoms at an altitude of 100 kilometers.
"When magnetic substorms occur, BBFs strike our atmosphere, making auroras shine," Cao explained.
BBFs contain electrons and other charged particles such as protons emanating from the magnetotail, a region of space on Earth's night-side where the sun's particle winds push Earth's magnetic field into a long tail, said the scientist.
At the tail's center is a denser region known as the plasma sheet. Violent changes in the plasma sheet are known as magnetic substorms. They last up to a couple of hours and somehow hurl electrons and protons earthward, Cao said.
According to Cao, the research team's next task is to build an aurora monitoring system, capable of forecasting and analyzing aurora movements.
(Xinhua News Agency September 8, 2006)
