Tag : Turbulence

Washington: Researchers have uncovered a previously hidden heating process that helps explain how the atmosphere that surrounds the Sun called the "solar corona" can be vastly hotter than the solar surface that emits it. The discovery at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) could improve tackling a range of astrophysical puzzles such as star formation, the origin of large-scale magnetic fields in the universe, and the ability to predict eruptive space weather events that can disrupt cell phone service and black out power grids on Earth. Understanding the heating process also has implications for fusion research. "Our direct numerical simulation is the first to provide clear identification of this heating mechanism in 3D space," said Chuanfei Dong, a physicist at PPPL and Princeton University who unmasked the process by conducting 200 million hours of computer time for the world's largest simulation of its kind."Current telescope and spacecraft instruments may not have high enough resolution to identify the process occurring at small scales," said Dong, who details the breakthrough in the journal Science Advances. The hidden ingredient is a process called magnetic reconnection that separates and violently reconnects magnetic fields in plasma, the soup of electrons and atomic nuclei that forms the solar atmosphere. Dong's simulation revealed how rapid reconnection of the magnetic field lines turns the large-scale turbulent energy into small-sale internal energy. As a consequence the turbulent energy is efficiently converted to thermal energy at small scales, thus superheating the corona. "Think of putting cream in coffee," Dong said. "The drops of cream soon become whorls and slender curls. ...