Thunderstorms

We still don't know quite a few things about thunderstorms, such as why one sometimes gets the red sprites shown in the linked picture. You can fly planes in and around them and the instruments tell us quite a bit, but they're so big our probes only catch a little of it.

I wonder if it is possible and useful to instrument a valley with chirping polarized radio transmitters and have receivers on planes or balloons measuring the Faraday rotation of the polarization axis. It isn't the same as a point measurement, since it integrates the magnetic effect along the whole path length (miles), but as the storm moves through the valley you'd get different sections through the storm, and maybe be able to tell if there were regions of exceptionally strong magnetic field.

If the Sun can have an effect on lightning rates, it might be nice to test models of how it works.