See, in my newly educated mode, (credits to Don Scott) ..
There is some credible, theoretical plasma physics basis behind his filament statement. (Dark mode Birkeland, filaments).
The problem is producing the evidence that one this big could ever exist, as Carl rightly points out.
How it powers itself is directly related to the density of the plasma and the power dissipation, as it travels thru space. At the moment in my 'education', it looks to me like a perpetual motion machine. It seems that once a Birkeland filament exists, it can never stop !
Cheers