Electric Currents along Astrophysical Jets
Research Center for Astronomy and Applied Mathematics, Academy of Athens, Athens 11527, Greece
National Research Nuclear University (MEPhI), 31 Kashirskoe Highway, 115409 Moscow, Russia
Academic Editors: Emmanouil Angelakis, Markus Boettcher and Jose L. Gómez
Galaxies 2017, 5(4), 71; https://doi.org/10.3390/galaxies5040071
Received: 14 July 2017 / Revised: 23 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
(This article belongs to the Special Issue Polarised Emission from Astrophysical Jets)
Astrophysical black holes and their surrounding accretion disks are believed to be threaded by grand design helical magnetic fields. There is strong theoretical evidence that the main driver of their winds and jets is the Lorentz force generated by these fields and their associated electric currents. Several researchers have reported direct evidence for large scale electric currents along astrophysical jets. Quite unexpectedly, their directions are not random as would have been the case if the magnetic field were generated by a magnetohydrodynamic dynamo. Instead, in all kpc-scale detections, the inferred electric currents are found to flow away from the galactic nucleus. This unexpected break of symmetry suggests that a battery mechanism is operating around the central black hole. In the present article, we summarize observational evidence for the existence of large scale electric currents and their associated grand design helical magnetic fields in kpc-scale astrophysical jets. We also present recent results of general relativistic radiation magnetohydrodynamic simulations which show the action of the Cosmic Battery in the vicinity of astrophysical black holes.