NASA determines what puts the "dance" into Northern Lights

William Atkins
Friday, 25 July 2008 02:44

Science - Space

According to the July 24, 2008 news release, NASA confirms that the THEMIS spacecraft have found that stressed out magnetic field lines are causing the colorful lights shows of the Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights) here on Earth.


THEMIS, or the acronym for "Time History of Events and Macroscale Interactions during Substorms", is a series of five NASA satellites. They were launched around the Earth to determine what was the origin of magnetic storms that turn the greenish Northern Lights (Aurora Borealis), in Earth’s northern hemisphere, and the Southern Lights (Aurora Australis), in the southern hemisphere of Earth, into dramatically colorful light shows.

THEMIS, launched on February 17, 2007, from the Cape Canaveral Air Force Launch Complex 17A, in Florida, U.S.A., aboard a Delta 2 rocket, was built by scientists at the Space Sciences Laboratory (SSL), from the University of California, Berkeley, and Swales Aerospace, now a part of defense and space system company Alliant Techsystems (ATK), headquartered in Minneapolis, Minnesota, U.S.A.

At the time the THEMIS mission was launched, Dr. Vassilis Angelopoulos, the THEMIS principal investigator and a research physicist at SSL, stated, "For over 30 years, the source location of these explosive energy releases has been sought after with great fervor. It is a question almost as old as space physics itself.”

Angelopoulos continues to explain, "A substorm starts from a single point in space and progresses past the moon's orbit within minutes, so a single satellite cannot identify the substorm origin. The five-satellite constellation of THEMIS will finally identify the trigger location and the physics involved in substorms." [UCBerkeley News: "NASA to launch THEMIS probes”]

A little bit over one year later, THEMIS has indeed discovered the origin of the Northern Lights. Dr. Angelopoulos states, “We discovered what makes the Northern Lights dance.” [NASA: “NASA satellites discover what powers northern lights”]

According to the NASA press release, THEMIS discovered. that “... explosions of magnetic energy a third of the way to the moon power substorms that cause sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights.”

The originating actions of the aurora involve a common process known to occur throughout the universe. The process is called “magnetic reconnection.” It involves the stretching of magnetic field lines, which eventually causes them to become stressed.

As they stretch (stress) the magnetic lines change their shape. Suddenly, when under too much stretch, they “snap” and produce the explosion that eventually causes the Northern Lights to suddenly brighten and move frantically about in the night sky.

David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center (Greenbelt, Maryland), explains, "As they capture and store energy from the solar wind, the Earth's magnetic field lines stretch far out into space. Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth's atmosphere. They create halos of shimmering aurora circling the northern and southern poles." [UCBerkeley News]

How specifically did the THEMIS orbiting satellites, and their partners on the ground, determine the source of the auroras? Please turn the page.