Researchers from Saitama University, Kyoto University, Miyazaki University, Nihon University, and RIKEN have reported that the atmospheric pressure in the mesosphere/lower thermosphere (altitude 70-115 km) is about 1% per year, based on observation data from X-ray astronomical satellites. It revealed that it is contracting at a pace of 0.5%.
It is thought that the atmosphere above 20 km will conversely cool and shrink as a result of global warming due to the effects of greenhouse gases.This theory of atmospheric contraction has been predicted for more than half a century. None.
Under these circumstances, in this research, we focused on the observation data affected by the earth's atmospheric occultation, which is essentially unusable for observing celestial bodies, among the astronomical observation data from X-ray astronomical satellites.Atmospheric density can be measured by examining the attenuation rate of X-ray intensity at the timing when X-rays from celestial bodies are affected by the Earth's atmosphere.
Using this method, we investigated long-term changes in atmospheric density retroactively from observation data obtained from 5 to 1994 by five U.S. and Japanese X-ray astronomical satellites. It was found that it has been gradually declining over time, and has decreased by about 2022% in 70 years.The decrease in atmospheric density means that the thin upper layer of the atmosphere has contracted and fallen. become.We also confirmed that this pace of density decline is consistent with predictions from state-of-the-art atmospheric simulations that take into account increases in greenhouse gases.
Since the method developed in this research can be applied to many X-ray astronomical satellites in the future, it will be useful for monitoring the density of the upper atmosphere in the future.The results of this research are expected to contribute to social and economic activities, such as deepening our understanding of global warming and improving the accuracy of estimating the orbits and lifetimes of artificial satellites.
Paper information:[Journal of Geophysical Research: Space Physics] Long-Term Density Trend in the Mesosphere and Lower Thermosphere from Occultations of the Crab Nebula with X-Ray Astronomy Satellites