The launch of NASA's science and engineering laboratory, Skylab, in 1973, heralded a new era of observations of the sun's corona from space. This was a major improvement over previous observations from eclipses or ground-based coronagraphs. You could see things in a new way, and in particular you could see the corona in X rays against the disk of the sun. What they had discovered was the magnetic field in the corona, with its closed and open regions. In the closed regions, magnetic field lines start at one point and come back to the sun at another to form a closed loop.
Open regions have field lines going out into space.
Open regions are called coronal holes, because they appear dimmer than the surrounding corona. In a few sessions, things that had puzzled everybody for decades just fell into place. Art received two NCAR Outstanding Publication Awards recognizing his efforts in the 1970s. Art became principal scientist on SMM, contributing analysis and theory that pointed to the magnetically closed regions in the corona as the probable source of these interplanetary shock waves. Some researchers still subscribe to the theory that solar flares are the cause of CMEs.