Would it be possible to use a magnetron beneath glider plane to generate its own thermals? Would it be feasible to install a series of magnetrons or something else on the underside of a gliders fuselage and wings in order to heat the air beneath the glider and ultimately cause the glider to obtain high altitude flight or obtain flight when thermals are not available? If hot air rises would you theoretically be able to artificially heat the air beneath a glider in order to achieve high altitude flight? 

I was watching videos about gliders and I noticed that thermal air pockets are often required to achieve altitude gain. I'm a dumb guy so excuse me if this is a ridiculously dumb question.
This would not be feasible.  First of all electromagnetic radiation emitted by magnetrons would heat up the water vapor in the air and not necessarily the air itself.  Molecules must have a dipole for EM heating to work.  Second it is not just the heat, what really creates the lift is the moving air upwards.  If you heat the air underneath the airplane that doesn't mean you will make the air move.  Thermals are typically less effective when close to the ground.  Thirdly, finding thermals on your own is part of the sport.  I think that generating your own thermal would defeat the concept of the sport.  

Also gliders don't have to completely rely on thermals to stay up.  Ridge Lift and Wave Lift can be used in mountainous areas where the lift is generated by a moderate wind slamming perpendicular to a mountain ridge forcing the air up.