The sun is entering the deepest minimum observed in the entire space era. There were no sunspots for most of 2018, and solar UV output has plummeted. At the same time, the latest satellite studies show how the upper atmosphere of the Earth responds to this drop in solar activity.
“We are seeing a cooling trend,” says Martin Mlynczak of NASA's Langley Research Center. “High above the earth's surface, near the edge of space, our atmosphere is losing thermal energy. If current trends continue, the Earth could soon set a space age record for cold.”
These results were obtained by NASA using the latest SABER instrument onboard NASA's TIMED satellite:
SABER controls the infrared emission of carbon dioxide (CO2) and nitric oxide (NO) molecules, two key elements that play a major role in the energy balance of the atmosphere at altitudes of 100-300 kilometers.
By measuring the infrared glow of CO2 and NO molecules, SABER can estimate the thermal state of the gas at the very edge of the atmosphere, which researchers call the thermosphere.
“The thermosphere always cools down during the solar minimum. This is one of the most important ways in which the solar cycle affects our planet,”explains Martin Mlinczak, who, in fact, leads the SABER project.
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As the thermosphere cools, it contracts, literally shrinking the radius of the earth's atmosphere. This thermodynamic shrinkage reduces the drag of satellites in low-Earth orbit, extending their lifespan. This is good news.
The bad news is that usually the thermosphere also slows down space debris, so after shrinkage this debris will remain in orbit for a long time. However, in fact, space debris that stops braking the thermosphere is, in general, the best news of the rest of the bad news.
To visually track changes taking place in the thermosphere, Mlinchak and his colleagues came up with the so-called TCI - the Thermosphere Climate Index, which clearly shows how much heat CO2 and NO molecules emit into outer space:
In interpreting this TCI visualization, Martin Mlinczak says that at the moment the infrared luminosity of NO, for example, is about 10 times less than in the more active phases of the solar cycle.
Unfortunately, the satellites of the TIMED satellite program and the analogs of the SABER instrument have been in orbit for about 17 years, so there are no complete TCI data for a century. However, based on the data of astronomers of past decades, we can say that the Earth is entering the Age of Cosmic Cold, an approximate analogue of which was observed in 1940:
However, researchers are optimistic as the last TIMED satellite was designed for just three years of operation. However, due to the cold compression of the thermosphere, TIMED satellite will hold out in its orbit for a very long time and the satellite will study the Age of Cosmic Cold in all details.
