Wednesday, July 30, 2008
Scientists have long puzzled about the phenomena of the auroras over the Earth's poles. The tremendous displays of light have been a source of mystery, wonder, speculation and myth since they were first observed.
Scientists using five satellites from NASA's THEMIS program (Time History of Events and Macroscale Interactions during Substorms) were recently able to say more about the source of these brilliant lights than was ever known previously. It has been known for some time that the auroras were caused by storms of charged particles. However, science had debated the source of these storms, local electrical disruptions in Earth's magnetic field or distant disturbances in the "magnetotail," the region of the Earth's magnetic field that points away from the sun.
A new study to be published next month in Science says: the storms of charged particles form when Earth's magnetic field lines collapse on each other, showering the upper atmosphere with captured radiation from the sun where it sparks the auroras.
These storms get their energy from the outflow of gases from the sun known as the solar wind. As it reaches Earth, the planet's magnetic field deflects the gases, although some is trapped and shunted toward the poles. When the charged molecules hit the oxygen and nitrogen in Earth's upper atmosphere, energy is released as captivating blue, green and red wavy displays of brilliance.