One day, when lighting force us to stay on earth. I asked my-self: "where are produced lightings?". This simple question has lead me to a pratical tool to detect convection current.
Lightning are produced when there is a difference of electric potential, which means that earth as a charge which is different from the could. Could are created from air masses coming from earth to the air. So how could we explain the difference of charge?
The Van-Der-Graaf generator illustrate nicely this case where the air is used to transfer electric charge between earth and coulds.
To validate this idea a testing instrument was mounted on an ASK-21. Based on a left-right course indicator, the instrument use two isolated copper wires of 0.2mm taped from the cockpit to the edge of each wings. Each wire is taped on the trailing edge and taped around the ailerons. At the edge of each wing, wires are free falling on 50 cm without any isolating cover.
The circuit on top of the course indicator is alimented by a 9 V battery and use an operational amplifier to compare the charge of the two wires. The result is send to the course indicator which should indicate the ascending current.
Until now, only one flight, in July 2001, have been made to check this instrument. The flight duration was 20 minutes and allowed to first remark that the charge assumption of the ascending current was wrong and then (by swaping the wing entries) it has indicated us to follow a could which was turning on top of us.
More testing should be done to verify this concept. If it does work, then the system should be coupled with front-back course indicator to locate more precisely where is located the core of the convention current.