Coronal hole
This sinister and dark shape spanning the active Sun is a coronal hole: a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Studied extensively in ultraviolet and X-rays from space from the 60s, coronal holes are known sources of fast solar wind electrons and atoms flowing into the space along open magnetic field lines. During periods of low activity, coronal holes typically cover regions located above the Sun's poles. But this coronal hole, one of the largest ever observed in the current cycle of solar activity, extends south pole (bottom) to the northern hemisphere. Coronal holes such that the latter may last a few solar rotations, until the magnetic fields are shifted and changing the configuration. false color visible, this image of the Sun was January 8, extreme ultraviolet by the EIT instrument onboard the SOHO space observatory.
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