Fast and slow winds, open and closed magnetism

Fast and slow winds, open and
    closed magnetism

. The solar atmosphere, or corona, is threaded with magnetic fields (yellow lines). Regions with open magnetic fields, known as coronal holes, give rise to fast, low density, solar wind streams (long, solid red arrows). In addition to permanent coronal holes at the SunŐs poles (top and bottom), coronal holes can sometimes occur closer to the SunŐs equator (center). Areas with closed magnetic fields yield the slow, dense wind (short, dashed red arrows). Comparisons of TRACE images with solar wind ACE data indicate that the speed and composition of the solar wind emerging from a given area have deep roots in the chromosphere. There is a shallow dense chromosphere below the strong, closed magnetic regions with a slow, dense, solar-wind outflow; deep, less dense chromosphere is found below the open magnetic regions with fast, tenuous, solar-wind outflow. This image was taken on 11 September 2003 with the Extreme-ultraviolet Imaging Telescope, abbreviated EIT, aboard the SOlar and Heliospheric Observatory, or SOHO for short. (Courtesy of the SOHO EIT consortium. SOHO is a project of international collaboration between ESA and NASA.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University