Why is the Corona so hot?

Why is the corona so hot? The rarefied corona, invisible from the Earth surface, stretches over the photosphere, i.e., over the visible surface of the sun. It is known that the corona is several times hotter, than the photosphere. For a long time astronomers assumed that the cause of such high temperature of the corona lies in the magnetic field, which keeps gigantic plasma loops high over the sun surface. Close supervision of coronal loops from TRACE satellite are to indicate the source of the corona energy more exactly. Devices at TRACE satellite obtain pictures of the sun in ultraviolet rays of very high energy. Based on these pictures a conclusion was made that considerable heating of the corona occurs in its lower layers, at the foundation of the loops, where plasma begins rising and goes back to the sun surface. The current striking picture from the TRACE demonstrates condensations of majestic hot coronal loops, which stretch upwards at 30 and more Earth diameters! Authors: M. Ashvaneni and others (Lockheed Martin Sun and Astrophysics Lab), TRACE, NASA.