Particle orbits and electric fields in astrophysical jets*

Astrophysical jets cannot power themselves so the power must come from
elsewhere. It was recently shown [1] that neutral-ion clumps having a
critical q/m in a weakly ionized protostellar accretion disk spiral
inwards and accumulate at small radius to produce a positively charged
cloud. Because the spiral motion depends on q/m,  electrons do not
similarly spiral in and, instead,  try to neutralize the positive charge
cloud by flowing along poloidal magnetic flux surfaces outside the disk.
This creates a complete poloidal electric current circuit where the inward
spiraling positive clumps are the power source and the jets are the load.
Toroidal magnetic field links the poloidal current so resultant J x B
forces drive bi-directional jets while also providing a Z-pinch
radial equilibrium. A radial EMF must supply the continuously increasing
toroidal flux in the lengthening, constant-current jets. Lorentz
transformation to the lab frame of Harris's Bennett pinch solution [2] supports
this point of view by showing that a Z-pinch moving with axial center of
mass velocity V_z has a lab-frame electric field E_r = V_zB_phi.

[1] P.M. Bellan, MNRAS 458 (2016) 4400; PPCF 60 (2018) 014006

[3] E. G. Harris, Nuovo Cimento 23 (1962) 115