Noctilucent clouds in relation to solar minimum

Photo from my shack window 12-06-2019 22UTC

I slowly realize that the bright noctilucent clouds sighting we saw was rare just like a bright aurora. Here in the Netherlands it even was a item in the 8 O'clock TV news. John MW1CFN wrote a excellent article on his weblog about the relation between NLC and PMSE and the expected propagation to Japan. Which was not happening the next morning, although it happened for stations in Finland! It would be great to find out why, after having such good visible NLC, we didn't have the propagation expected. But I guess it will remain a mystery and a guess. Another thing believed and still under research is the relation between the solar minimum and NLC. It is generally believed that as the sun goes to solar minimum, the solar heating of the atmosphere decreases, and a cooling trend would be expected. In order to form noctilucent clouds three things are needed:  very cold temperatures, water vapor and meteoric dust. The meteoric dust provides sites that the water vapor can cling to until the cold temperatures cause water ice to form.