Electrical currents born from thunderstorms are able to flow through the atmosphere and around the globe, causing a detectable electrification of the air even in places with no thunderstorm activity.
But until recently, scientists have not had a good understanding of how conductivity varies throughout the atmosphere and how that may affect the path of the electrical currents. Now, a research team led by the University of Colorado Boulder has developed a global electric circuit model by adding an additional layer to a climate model created by colleagues at the National Centre for Atmospheric Research (NCAR) in Boulder.
The results, published in the Journal of Geophysical Research, show that the atmosphere is generally less conductive over the equator and above Southeast Asia and more conductive closer to the poles, though the atmosphere’s conductivity changes seasonally and with the weather.
Research into atmospheric electrification stretches back to the 1750s, when researchers, including Benjamin Franklin, were trying to better understand the nature of lightning. In the 1800s, scientists measured changes in the atmosphere’s electric field from the Kew Observatory near London, and in the 1900s, the Carnegie, an all-wooden ship built without any magnetic materials, crisscrossed the ocean while taking atmospheric electricity measurements that are still referenced today.
But obtaining a global picture of atmospheric conductivity has been difficult, in part because the atmosphere’s ability to channel electricity is not static. Ions, which allow current to move through the air, are added to the upper atmosphere by a continuous bombardment of galactic cosmic rays and to the lower atmosphere through radioactive decay. But those ions can be removed from the atmosphere in a variety of ways.