March 27, 2001
'Cannibals' in Space:
CUA Scientists Find Interaction Between Solar Eruptions
Scientists from NASA and Catholic University's Center for Solar Physics and Space Weather at the Institute for Astrophysics and Computational Sciences have discovered a "cannibalistic" feature of solar eruptions, magnetic storms with the potential to disrupt power grids, pipelines and communication systems on Earth.
The eruptions, magnetic clouds issuing from the sun, have the capacity to overtake and "eat" each other while traveling toward Earth. The consumptive process can make such storms faster and larger, affecting scientists' ability to track them and estimate their time of arrival.
Called coronal mass ejections (CMEs), the solar eruptions headed toward Earth are potentially harmful to advanced technology; cannibal CMEs that cross Earth's path may result in longer magnetic storms near the planet.
"We're trying to understand the complex propagation of CMEs through the interplanetary medium," said Dr. Natchimuthuk Gopalswamy, lead author of a research paper presented today during a meeting of the European Geophysical Society in Nice, France. Gopalswamy, a research professor with Catholic University's Institute for Astrophysics and Computational Sciences, is stationed at NASA's Goddard Space Flight Center, Greenbelt, Md. He presented the research with his colleagues from Goddard, CUA and the Naval Research Laboratory. The cannibalism will seriously affect the expected arrival times of CMEs in the vicinity of Earth, he said.
Astronomers first detected the solar "cannibals" when strange radio fireworks were first heard by the team using NASA's "Wind" spacecraft. Researchers connected the fireworks to CME collisions when they linked the timing of the radio outbursts to images of solar eruptions consuming each other captured by the Solar and Heliospheric Observatory spacecraft from NASA and the European Space Agency.
Coronal mass ejections are clouds of electrified, magnetic gas, weighing billions of tons, ejected from the Sun and hurled into space at speeds of 12 to 1,250 miles per second. Depending on the orientation of the magnetic fields carried by the ejection cloud, Earth-directed eruptions cause magnetic storms by interacting with the Earth's magnetic field, distorting its shape and accelerating electrically charged particles trapped within.
The researchers believe cannibal eruptions may be the source of "complex ejecta" CME clouds, larger and more complex in structure than typical eruptions. These traits cause complex ejecta CMEs to trigger protracted magnetic storms when they envelop the Earth.
Severe solar weather is often heralded by dramatic auroral displays (northern and southern lights), but magnetic storms are occasionally harmful, potentially affecting satellites, radio communications and power systems. Understanding what happens to ejection clouds on their way to Earth is important in assessing their impact on the near-Earth space environment.
Observations from Wind's Radio and Plasma Wave experiment revealed occasional intense bursts of emission originating far away from the Sun. When Gopalswamy and his colleagues were searching for the source of these radio outbursts, they discovered the ejection interaction, which produces high-energy electrons and causes the radio outbursts. Twenty-one cannibalistic ejections have been identified since the initial discovery in April of 1997. More events may have gone undetected because they are less energetic and do not produce a radio outburst, according to the researchers.
The astronomers expect an increased rate of ejection interaction during the current peak in the 11-year cycle of violent solar activity, called solar maximum, because more ejections are expelled in quick succession during a solar maximum. During solar minimum, only one ejection per every other day is common; during maximum, several ejections occur in a day.
For images and other background information, visit: http://www.gsfc.nasa.gov/GSFC/SpaceSci/sunearth/cannibalcme.htm
Revised: March 27, 2001
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