Research Spotlight: Low solar activity explains contracted thermosphere


  • Ernie Tretkoff


From 2007 to 2009, the outermost layer of the atmosphere, the thermosphere, was abnormally cool and contracted, with lower than normal densities at altitudes near 400 kilometers. In fact, the thermosphere's density, determined by measuring the drag on satellites, was lower during this period than at any time since the beginning of the space age.