A non-negligible fraction of a Supermassive Black Hole ’ s ( SMBH ) rest mass energy gets transported into extragalactic space by a remarkable process in jets which are incompletely understood .
What are the physical processes which transport this energy ?
It is likely that the energy flows electromagnetically , rather than via a particle beam flux .
The deduced electromagnetic fields may produce particles of energy as high as \sim 10 ^ { 20 } eV .
The energetics of SMBH accretion disk models and the electromagnetic energy transfer imply that a SMBH should generate a 10 ^ { 18 } -10 ^ { 19 } Ampères current close to the black hole and its accretion disk .
We describe the so far best observation-based estimate of the magnitude of the current flow along the axis of the jet extending from the nucleus of the active galaxy in 3C303 .
The current is measured to be I \sim 10 ^ { 18 } Ampères at \sim 40 kpc away from the AGN .
This indicates that organised current flow remains intact over multi-kpc distances .
The electric current I transports electromagnetic power into free space , P = I ^ { 2 } Z , where Z \sim 30 Ohms is related to the impedance of free space , and this points to the existence of cosmic electric circuit .
The associated electric potential drop , V = IZ , is of the order of that required to generate Ultra High Energy Cosmic Rays ( UHECR ) .
We also explore further implications , including disruption/deflection of the power flow and also why such measurements , exemplified by those on 3C303 , are currently very difficult to make and to unambiguously interpret .
This naturally leads to the topic of how such measurements can be extended and improved in the future .
We describe the analogy of electromagnetically dominated jets with transmission lines .
High powered jets in vacuo can be understood by approximate analogy with a waveguide .
The importance of inductance , impedance , and other laboratory electrical concepts are discussed in this context .
To appear in Proc .
18th International Symposium on Very High Energy Cosmic Ray Interactions ( ISVHECR2014 ) , CERN , Switzerland