by Dr. Tony Phillips
TCI is a number published daily by NASA, which tells us how hot Earth's upper atmosphere is.
The thermosphere, our atmosphere's highest layer, literally touches space and is a sort of "first responder" to solar activity. Hunt created this above plot showing how TCI has unfolded during the last 7 solar cycles.
Solar Cycle 25 (shown in blue - above image) is just getting started:
If this trend
continues, the thermosphere could soon hit a 20-year high in
Here on the planet's surface we do not feel its heat:
As Dr. Marty Mlynczak of NASA notes,
As far as we know, cyclical warming and cooling of the thermosphere by the solar cycle does not affect climate.
Nevertheless, the thermosphere is important.
Almost 40 Starlink satellites fell out of the sky earlier this year as a result of aerodynamic drag up there...
TCI might also have some predictive value.
Hunt's plot shows that the index is on an upward trajectory that most closely mimics Solar Cycle 20, which peaked back in the 1970s. Solar Cycle 20 was an above average solar cycle with plenty of solar activity.
Coincidentally, a new prediction for Solar Cycle 25 based on the arrival of the Termination Event suggests the same thing:
You can follow the progress of TCI as Solar Cycle 25 unfolds.
It is published every day right here on Spaceweather.com.