TL;DR: As of March 2019, we have not yet reached the minimum of the current solar cycle. But we are close.
Above: An historical record of the Thermosphere Climate Index. Mlynczak and colleagues recently published a paper on the TCI showing that the state of the thermosphere can be discussed using a set of five plain language terms: Cold, Cool, Neutral, Warm, and Hot.
“Right now, it is very low indeed,” says Mlynczak. “SABER is currently
measuring 33 billion Watts of infrared power from NO. That’s 10 times
smaller than we see during more active phases of the solar cycle.”
As 2018 comes to an end, the Thermosphere Climate Index is on the
verge of setting a Space Age record for Cold. “We’re not there quite
yet,” says Mlynczak, “but it could happen in a matter of months.”