Space weather: Looking at the heart of explosions on the Sun

Thanks to two NASA spacecraft, astronomers have put together an amazing movie that details the once-mysterious process of magnetic reconnection, which is what happens at the heart of all explosions on the Sun. This process occurs when magnetic field lines come together, break apart, and then exchange partners and then snap into new positions, which releases magnetic energy. It also creates phenomena like solar flares and coronal mass ejections that fling radiation across the solar system.

Understanding this process helps scientists with providing warnings of this kind of space weather, which affects satellites near Earth and interferes with radio communications. It is usually very difficult to study because magnetic fields are invisible to optical instruments like conventional telescopes. The magnetic fields, however, naturally force the Sun's charged plasma to course along their length. Telescopes can see that material as bright lines looping and arcing through the Sun's atmosphere, which allows scientists to map out the magnetic field lines.

Yang Su, a solar scientist at the University of Graz in Austria, discovered this when he began to study images of magnetic reconnection from NASA's Solar Dynamics Observatory (SDO) as it was happening on the Sun. In the images, Su noticed two bundles of field lines moving towards each other, meeting briefly to form a shape similar to an "X" and then shooting apart with one set of lines and its particles leaping into space and one set falling back down on the Sun.

To confirm what Su saw, he turned to the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). RHESSI collects spectrograms, a kind of data that can show where exceptionally hot material is present during events on the Sun. The RHESSI data showed hot pockets of solar material forming above and below the reconnection point, which is a signature occurrence of such an event. By combining data from both SDO and RHESSI, the scientists described the process of what they were seeing.

“This is the first time we’ve seen the entire, detailed structure of this process, because of the high quality data from SDO,” Su said. “It supports the whole picture of reconnection, with visual evidence.”

Learning more about magnetic reconnection helps scientists understand not just what happens on the Sun, but also similar processes that happen near Earth and within our magnetosphere. NASA plans to launch the Magnetosphere Multiscale (MMS) mission in late 2014 to take a closer look at magnetic reconnection in space. By using multiple spacecraft, scientists hope to better understand the space weather that affects our own planet.


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