Uranus' Long‐Term Thermospheric Cooling Is Unlikely to Be Primarily Driven by the Solar Wind

Abstract Over the last 40 yrs, Uranus' thermospheric temperature has decreased by ∼8 K/yr. Here we show that this is less likely to be driven by solar wind kinetic power than previously thought. We determine that the solar wind kinetic power at Uranus has been increasing since the start of solar cycle 24 in 2009, while Uranus's thermospheric temperature has continued to decline. A comparison of the ascending phases of solar cycles 24 and 25 shows an increase in solar wind power of 15%, while Uranus's thermospheric temperature decreased by 18% in the same timeframe. If the solar wind was a driver of thermospheric temperature at Uranus it would be expected that Uranus would have reversed its declining temperature trend in recent years. We have also estimated that a decline in energy sourced from the solar wind would not be sufficient to change the thermospheric temperature by the level observed.