Coronal Holes (IMAGE) DOE/Princeton Plasma Physics Laboratory Caption An image showing two coronal holes, depicted as relatively dark regions. Coronal holes are lower density and temperature regions of the sun’s outer atmosphere, known as the corona. Credit NASA/Goddard/SDO Usage Restrictions N/A License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.