Uranus' Long-term Thermospheric Cooling is unlikely to be primarily driven by the Solar Wind

Over the last 40 years, Uranus’ thermospheric temperature has decreased by ~8K/yr. Here we show that this is unlikely to be driven by the weakening solar wind. We have estimated that the expected energy change from the solar wind would not be sufficient to change the thermospheric temperature. We also show that the solar wind kinetic power has been increasing since 2008, while Uranus’s thermospheric temperature has continued to decline. Since 2008, a fitted trend shows a change in the solar wind kinetic power at Uranus of +28% while the thermospheric temperature changed by -29%. A comparison of the ascending phases of solar cycles 24 and 25 also show an increase in solar wind power of 15%, with a decrease in temperature of 18%. If the solar wind was a driver of thermospheric temperature at Uranus it would be expected that Uranus would have reversed its declining temperature also.