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For the first time Man has been able to (almost) simultaneously observe the entire solar surface. This has been made possible by the twin probes of STEREO (Solar TErrestrial Relations Observatory) that precede and trail Earth in its orbit, and are currently located about 180 degrees apart.
This configuration allows the two probes to observe what is happening in two different solar hemispheres, half of each being invisible from Earth. By joining these two halves it has been possible to make the image above to the left, showing the other side of the Sun, with evolving active regions in white.
The thin dark stripe corresponds to the solar limb as seen by the two probes, and will be filled in over the next few days.
Up until now it has only been possible to guess what was happening on the other side of the Sun via complex helioseismological models. Now we can see it directly.
The image to the right, on the other hand, shows a wave-like structure along one side of a plasma cloud, violently expelled from the Sun in a so-called CME (Coronal Mass Ejection). This picture is from the the Atmospheric Imaging Assembly (AIA) experiment on NASA's Solar Dynamics Observatory (SDO), and has been analysed by a team led by Claire Foullon at the Centre for Fusion Space and Astrophysics (University of Warwick).
Such a structure has never been observed before, probably because the images have been made in the extreme ultraviolet, that traces gas at temperatures around 11 million Kelvin.
The origin of these wrinkles, reminiscent of the turbulent structures seen at the edges of the cloud bands on Jupiter, are caused by bodies of fluid moving past eachother at different speeds.
The sheer in the interface creates an instability that results in "waves", in this case visible in the material of the CME as it moves through the gas of the solar corona. A similar effect on Earth, between air and water, creates ocean waves.
In the case of the Sun it is particularly interesting because it could finally explain why CMEs often curve, despite being initially straight: the curve would be caused by the braking effect caused by the transfer of energy to the corona on one side of the CME. Why this should happen only on one side remains a mystery however.
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