Spring Break
Probes capture 3-D images of solar explosions
Issue date: 4/30/09
Researchers using data from NASA probes have discovered that a certain type of solar storm looks like a croissant! NASA's Solar Terrestrial Relations Observatory (STEREO) probes, a pair of spacecraft tracking solar weather, are allowing scientists to track the speed, trajectory and 3-D shape of solar explosions, known as coronal mass ejections, as they leave the sun, improving our ability to forecast solar weather.
"Coronal mass ejections (CMEs for short) are solar 'hurricanes' that erupt from the sun's surface and spew billions of tons of plasma into space at speeds of thousands of miles per hour," said Kristi Marren, public affairs representative for the Hopkins Applied Physics Laboratory (APL).
"Aside from creating auroral lights, when these massive storms hit our atmosphere they can disrupt satellite communications, GPS and cell phone signals and can cause power outages or blackouts," Marren said.
As a result, tracking solar weather is crucial; If we know when these disruptions are likely to occur, we can manage them more effectively and be more prepared for their arrival.
Angelos Vourlidas, a researcher at the Naval Research Lab who developed the croissant model for CMEs, said, "Before the STEREO probes, measurements and the subsequent data of a CME observed near the sun had to wait until the ejections arrived at Earth three to seven days later. Now we can see a CME from the time it leaves the solar surface until it reaches Earth, and we can reconstruct the event in 3-D directly from the images."
From this reconstruction, he realized that CMEs are shaped like a series of twisted magnetic fields, fat in the middle and thin on the edges ÂÂ- in short, a croissant.
According to Vourlidas, the twisted shape of CMEs makes sense. "CMEs get started as twisted ropes of solar magnetism. When the energy in the twist reaches some threshold, there is an explosion which expels the CME away from the sun," he said.
This model, along with the vantage point offered by the STEREO satellites, allows improved forecasting of solar weather. "We believe we can now predict when a CME will hit Earth with only three hours of uncertainty, a four-fold improvement over older methods," Vourlidas said.
"Coronal mass ejections (CMEs for short) are solar 'hurricanes' that erupt from the sun's surface and spew billions of tons of plasma into space at speeds of thousands of miles per hour," said Kristi Marren, public affairs representative for the Hopkins Applied Physics Laboratory (APL).
"Aside from creating auroral lights, when these massive storms hit our atmosphere they can disrupt satellite communications, GPS and cell phone signals and can cause power outages or blackouts," Marren said.
As a result, tracking solar weather is crucial; If we know when these disruptions are likely to occur, we can manage them more effectively and be more prepared for their arrival.
Angelos Vourlidas, a researcher at the Naval Research Lab who developed the croissant model for CMEs, said, "Before the STEREO probes, measurements and the subsequent data of a CME observed near the sun had to wait until the ejections arrived at Earth three to seven days later. Now we can see a CME from the time it leaves the solar surface until it reaches Earth, and we can reconstruct the event in 3-D directly from the images."
From this reconstruction, he realized that CMEs are shaped like a series of twisted magnetic fields, fat in the middle and thin on the edges ÂÂ- in short, a croissant.
According to Vourlidas, the twisted shape of CMEs makes sense. "CMEs get started as twisted ropes of solar magnetism. When the energy in the twist reaches some threshold, there is an explosion which expels the CME away from the sun," he said.
This model, along with the vantage point offered by the STEREO satellites, allows improved forecasting of solar weather. "We believe we can now predict when a CME will hit Earth with only three hours of uncertainty, a four-fold improvement over older methods," Vourlidas said.
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