Long-Term Density Trend in the Mesosphere and Lower Thermosphere from Occultations of the Crab Nebula with X-Ray Astronomy Satellites

Abstract

Time series of combined O and N densities are measured in the MLT, based on atmospheric occultations of the Crab Nebula using X-ray astronomy satellites.• The density is decreasing everywhere, with a local minimum of −12%/decade near 105 km.• The local minimum in density trends may be due to strong cooling by water vapor and ozone, as was first predicted by Akmaev et al. (2006).