July 4, 2012
Doppler Techniques Could Help Predict Solar Storms
Lee Rannals for redOrbit.com - Your Universe Online
Scientists are using Doppler techniques that may be able to take predicting space weather to a new level and understanding.
An international team of researchers have combined Doppler techniques with images and data from a space-based telescope to observe loops of 1,800,000-degree Fahrenheit plasma flowing up from the sun's surface at more than 12 miles per second.
These loops arch over the sun, and may be the first signs of trouble spots where plasma undergoes "impulsive heating," according to the researchers.
The team said they expect their findings to help scientists understand the genesis of solar flares and coronal mass ejections (CMEs), which threaten satellites orbiting the Earth through solar storms.
The team wrote in the Astrophysical Journal Letters that Doppler measurements drawn from images taken by the Extreme-ultraviolet imaging Spectrometer (EIS) aboard the Hinode solar satellite show the first observation of a "warm loop," which is when plasma rises from the surface of the sun rather than sinks back into it.
In visible light, Doppler objects moving away from the viewer are shifted red, while objects that move closer shift blue.
Doppler techniques have been useful to astrophysicists in judging how fast other stars, and even galaxies, are moving in an expanding universe.
In previous observations of active regions of the sun, warm loops like the one observed by the team have been seen to shift red and, the plasma was thought to be sinking.
Astronomers believe that heating is taking place high in the sun's atmosphere, leading to the evaporation of material from near the surface into the atmosphere that then flows back down as it cools.
“The blue shifts are the signature, or ℠smoking gun,´ of plasma flowing up into the atmosphere,” Stephen Bradshaw, Rice University's William V. Vietti Junior Chair of Space Physics who worked on the study, said in a press release. “They show that the fastest up-flows are found near the surface of the sun. This information gives us clues to the location where the heating is taking place, how fast it is and how much energy is needed.”
Richard Harrison, head of space physics and chief scientist at the Rutherford Appleton Laboratory in the United Kingdom, said that the sun's solar active regions are what drive extreme conditions leading to explosive flares and the huge eruptions.
He said "understanding these active regions is absolutely critical for the study of what we now call space weather."
Bradshaw said the sun is closing-in on its 11-year cycle, when flares and CMEs occur most frequently.
“These events present the most danger to satellites, power grids and even to airliners on flight paths in polar regions,” Bradshaw said in the release. “This period is called solar maximum, and we will become ever more reliant on this technology during every subsequent solar cycle."
He said one of the goals of the research is to develop a space-weather forecasting capability, where solar storms can be predicted by detecting them before they even occur at the sun.
“This is much like monitoring depressions as precursors to tropical storms and hurricanes, but space-weather forecasters will monitor active regions," Bradshaw said in the release. "Accurate forecasts of solar storms will give us the maximum possible time to prepare for their arrival at Earth and to mitigate their effects."
Image 2 (below): Left, image of hot (1.8-million degree Fahrenheit) active region loops. Right, flows of solar plasma (blue shifts). Credit: Left: SDO/AIA (NASA). Right: Hinode/EIS (JAXA, NASA, ESA and STFC)