Scientists revealed that a big chunk of our thermosphere “collapsed” in 2008-2009. How come we didn’t feel it?

Question by Sky: Scientists revealed that a big chunk of our thermosphere “collapsed” in 2008-2009. How come we didn’t feel it?
An upper layer of Earth’s atmosphere recently collapsed in an unexpectedly large
contraction, the sheer size of which has scientists scratching their heads, NASA
announced Thursday.

The layer of gas – called the thermosphere – is now rebounding again. This type
of collapse is not rare, but its magnitude shocked scientists.

“This is the biggest contraction of the thermosphere in at least 43 years,” said
John Emmert of the Naval Research Lab, lead author of a paper announcing the
finding in the June 19 issue of the journal Geophysical Research Letters. “It’s
a Space Age record.”

The collapse occurred during a period of relative solar inactivity – called a
solar minimum from 2008 to 2009. These minimums are known to cool and contract
the thermosphere, however, the recent collapse was two to three times greater
than low solar activity could explain.

“Something is going on that we do not understand,” Emmert said.

The thermosphere lies high above the Earth’s surface, close to where our planet
meets the edge of space. It ranges in altitude from 55 miles (90 km) to 370
miles (600 km) above the ground. At this height, satellites and meteors fly and
auroras shine. [Graphic: Earth’s Atmosphere Top to Bottom]

The thermosphere interacts strongly with the sun, so is very affected by periods
of high or low solar activity. This layer intercepts extreme ultraviolet light
(EUV) from the sun before it can reach the ground.

When solar activity is high, solar EUV warms the thermosphere, causing it to
puff up like a marshmallow held over a camp fire. When solar activity is low,
the opposite occurs.

Recently, solar activity has been at an extreme low. In 2008 and 2009, sunspots
were scarce, solar flares almost non-existent, and solar EUV radiation was at a
low ebb.

Still, the thermospheric collapse of 2008-2009 was not only bigger than any
previous collapse, it was also bigger than the sun’s activity alone could
explain.

To calculate the collapse, Emmert analyzed the decay rates of more than 5,000
satellites orbiting above Earth between 1967 and 2010. This provided a
space-time sampling of thermospheric density, temperature, and pressure covering
almost the entire Space Age.

Emmert suggests carbon dioxide (CO2) in the thermosphere might play a role in
explaining the atmospheric collapse.

This gas acts as a coolant, shedding heat via infrared radiation. It is
widely-known that CO2 levels have been increasing in Earth’s atmosphere. Extra
CO2 in the thermosphere could have magnified the cooling action of solar
minimum.

“But the numbers don’t quite add up,” Emmert said. “Even when we take CO2 into
account using our best understanding of how it operates as a coolant, we cannot
fully explain the thermosphere’s collapse.”

The researchers hope further monitoring of the upper atmosphere will help them
get to the bottom of the situation.

Best answer:

Answer by Urwumpe
Because the Thermosphere is very thin, it is the layer from 85 km altitude to 1500 km – there are only a few thousand atoms per cubic centimeter in it.

What do you think? Answer below!