Northern Lights' Source Found in Giant 'Magnetic Ropes'

An eight-month old NASA mission to unravel the source of the Northern Lights' energy has made startling progress, discovering giant magnetic "ropes" that connect the Earth to the Sun.

The NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission consists of five separate satellites, along with supporting ground-based cameras. This system began observing an enormous substorm, or Northern Light event, on March 23, which helped trigger the discoveries.

The storm moved faster than anyone had expected, crossing 15 degrees of longitude in a single minute, about 400 miles per hour. The entire two-hour event released about five hundred thousand billion Joules, or about as much energy as a magnitude 5.5 earthquake, researchers said.

Which, well and good, but where did the energy come from?

Over the next few months, the spacecraft encountered what researchers call magnetic ropes, essentially bundles of magnetic fields that are twisted together like twine. The first to be mapped by the THEMIS satellites was located about 40,000 miles above the Earth's surface, in the magnetopause, and about as wide as the Earth itself.

The magnetopause is the region where the solar wind – electrically charged particles that flow away from the sun at incredible speeds –
crashes into the Earth's magnetic field. The "rope" formed there and unraveled again over the course of just a few minutes, but in the process proved to be a significant conduit for solar wind energy.

Here's researcher David Sibeck, project scientist for the mission at NASA's Goddard Space Flight Center.

"The satellites have found evidence of magnetic ropes connecting
Earth's upper atmosphere directly to the sun," Sibeck said. "We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras."

The scientists have also observed the equivalent of a "bow shock," as at the leading edge of a boat, where the front edge of Earth's magnetic field first encounters the solar wind. Occasionally a burst of electrical current in the solar wind will hit this "bow shock,"
creating an explosion, researchers said.

The team's early findings will be presented at the annual meeting of the American Geophysical Union in San Francisco in this month.

NASA Spacecraft Make New Discoveries About Northern Lights [NASA press release]

(Image: The eerie shimmer of the Northern Lights. Credit: NASA)