A New View of the Magnetic Sun

Abstract

Developments in instrumentation, numerical simulations, and theory are rapidly changing our view of solar magnetism. There are now observations that show magnetic field emerging on all convective scales. The emergence rate replaces the quiet Sun flux in less than 12 hours and even active region and sunspot fields are replaced in less than a month. There is evidence for local dynamo action suggesting that a bottom to a convection zone is not required for stellar magnetic activity. It is now recognized that 3D magnetic reconnection is fundamentally different from 2D. Time sequences of the one arc second spatial resolution TRACE images show that the temperature and density structure of the corona changes as fast as radiation and conduction allow. Because adjacent loops are observed in a range of temperatures that span at least 30 000 to 2 500 000 K, there is a inter mixture of temperatures regimes throughout the corona. Consequently, there is no line of sight through the corona that can be characterized by a single temperature and density. It would be surprising if other stars or other astrophysical systems with magnetic fields were simpler than the solar atmosphere.