Next month, the Japanese space agency, JAXA, will pilot its 'electrodynamic tether' for the first time. It is one of many possible solutions that have been proposed to deal with space debris"
I don't understand how they propose to deal with the tremendous delta-V that is the inherent problem with space junk. The issue is not "space is full of nuts and bolts" it's "space is full of nuts and bolts that are going your orbital speed but at 70 degrees to your orbit therefore they're coming at you a little faster than a 9mm parabellum."
Unless you're imparting a magnetic force directly aligned with that particular object's trajectory, though, you're not going to slow it down - you're going to deflect it. The orbit it was on is now that orbit X (cross - vector math) the vector of the magnetic force. I'm not saying they didn't think this through - we are talking about rocket scientists here. I just wish the article had done a better job of explaining.