Coronal Mass Ejections Are Massive solar eruptions

Massive solar eruptions called coronal mass ejections (CMEs) are among the most important events in space for scientists to understand. When directed at Earth, CME’s can disrupt radio communications, satellites, and power grids. While we have satellites in space and observatories on the ground to track these CMEs, scientists can now image them in three-dimensions (3D). These new views are created from ordinary two-dimensional images from the Solar and Heliospheric Observatory (SOHO) spacecraft.

Right: Coronal mass ejection imaged in three dimensions from data obtained by the SOHO spacecraft.

“We need to see the structure of CMEs in three dimensions to fully understand their origin and the process that launches them from the Sun,” said Dr. Thomas Moran of the Catholic University of America, Washington, DC. “Views in three dimensions will help to better predict CME arrival times and impact angles at the Earth.”

CMEs blast billions of tons of electrified gas from the Sun’s atmosphere into space at millions of miles per hour. Researchers believe CMEs are launched when solar magnetic fields become strained and suddenly “snap” to a new configuration, like a rubber band that has been twisted to the breaking point. Complex and distorted magnetic fields travel with the CME cloud and sometimes interact with the Earth’s own magnetic field to pour tremendous amounts of energy into the space near Earth.

Left: The researchers imaged both halo and loop CMEs, defined by the perspective of the viewer. Halo CMES, like this one, provide a front or rear view of the eruption as it heads toward Earth. Credit: NASA/ESA

The magnetic fields are invisible, but because the CME gas is electrified (a plasma), it spirals around the magnetic fields, tracing out their shapes. A view of the CME gas in three dimensions gives scientists valuable information on the structure and behavior of the magnetic fields powering the CME.

Right: Halo CMEs can be heading toward or away from Earth. The colors represent the distance from the plane of the Sun; in other words, the distance from the Earth. Credit: NASA/ESA

With the new analysis technique for SOHO data, the team has confirmed that the structure of Earth-directed CMEs is an expanding arcade of loops, rather than a bubble or rope-like structure. Although the CME eventually disconnects from the Sun, the team also discovered that the loops remained connected to the source region for an unexpectedly long time, at least as long as the CME was visible to the SOHO instrument.

Scientists believe this new method will complement the upcoming Solar Terrestrial Relations Observatory mission, scheduled for launch in February 2006, which will use two widely separated spacecraft to construct 3D views of CMEs by combining images from the different vantage points of the twin spacecraft.