I'm taking this with a grain of salt. It's popular for fringe scientists to assert that gravity can be controlled via electromagnetism. I've seen a couple UFO schematics online over the years that use electromagnetism to play with gravity and produce thrust.

Also, my understanding of gravity is that it really isn't a force at all, but rather a warping of spacetime by an object with mass, which makes the concepts of a field a bit strange to me...