The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) is designed to provide an unprecedented view of the solar corona, taking images that span at least 1.3 solar diameters in multiple wavelengths nearly simultaneously.
he AIA 193 channel takes images of the Sun at 193 angstroms (extreme ultraviolet) which highlights the outer atmosphere of the Sun – called the corona – as well as hot flare plasma. Hot active regions, solar flares, and coronal mass ejections will appear bright here. The dark areas ‒ called coronal holes ‒ are large regions in the corona that are less dense and cooler than surrounding areas. Coronal holes are where the Sun's magnetic field does not loop back down to the surface; it is open into interplanetary space. They are places where very little radiation is emitted, yet are the main source of solar wind particles. The open structure of their magnetic field allows a constant flow of high-density plasma to stream out of the holes.
This is an image of the Sun observed by Solar Dynamics Observatory in the extreme ultraviolet region (193 Å) on 2013-03-04 at 23:45:07 UT. At this time, some of the coronal holes are directed towards the Earth. Since coronal holes are often the source of strong solar wind gusts that carry solar particles into interplanetary space, an increase in solar wind activity over the next days is expected. Solar wind flowing from the indicated coronal hole should reach Earth on March 07-08.
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