Ozone Beam
A smaller scale version of space solar power might be able to pulse microwaves to create ozone between 20 km and 50 km altitude. If the beam was 10 km high and 100 km wide, the transmitter could be aimed from GEO towards the limb of the Earth over Antarctica, where scattering will have few biological consequences.
The polar radius is 6353 km; assume this radius out to the edge of Antarctica. A right triangle with a hypoteneuse of 42164 km and one side 6353 + 25 = 6378 km (in the lower polar stratosphere) will occur at arccos( 6378 / 42164 ) = 81.3 °S latitude, over unpopulated continental Antarctica.
