Unfortunately, astronomy has become so specialized that there are a lot of professional astronomers who don't know about these mechanisms. Maybe they need a little refresher course in this topic to prevent them from making grossly inaccurate statements about the role of electric fields in cosmic processes.
This mechanism of charge separation and resulting electric field generation was first recognized back in the 1920s. Gravitational stratification of plasma gives light electrons a larger scale height than heavy ions. This generates a weak charge separation and small electric field, forming a structure similar to a weak double layer. The presence of dust can significantly strengthen the field. There are a number of astrophysical environments where this process is believed to act:
- solar atmosphere and out into the solar wind
- planetary ionospheres. This configuration contributes to the Birkeland currents identified in planetary magnetospheres.
- galactic disk 'atmospheres'
- possible source of seed fields for stellar dynamo processes
A dipole magnet at rest just produces a magnetic field. But if the dipole is rotated and the magnetic axis of the dipole is tilted from the rotation axis, the magnetic field at any point near the magnet changes, which by Maxwell's equations, produces an electric field. Because Maxwell's equations are Lorentz invariant, the easiest way to find the values of this electric field is to transform the magnetic dipole into a rotating coordinate system. This system is a popular demonstration of how to treat relativity in rotating coordinate systems and dates back to the 1930s. Here's some areas in the astrophysical literature where this process is important:
- Pulsars: The strong magnetic fields of fast-rotating neutron stars (~10^10 gauss) generate very strong electric fields in the charged plasma environment around them.
- Ionospheric & Magnetospheric physics. This configuration is another contribution to the Birkeland currents identified in planetary magnetospheres.
Charge-separation by radiation pressure: Photons interact with electrons more strongly than protons and can accelerate electrons away.
- Driver of stellar winds. In the stellar wind outflow, the electrons will get an extra boost outward due to momentum transfer by scattering from the outflowing photons.
- Gamma-ray bursts: High-energy photons can create a charge separation in the interstellar medium (ISM)
Black Hole Electrodynamics
When ionized plasma accretes on a black hole, the external observer never sees the material cross the event horizon. Instead, the material forms a thin layer of hot plasma just outside the event horizon. This layer acts like a conducting metal shell around the object. Seeded with even small magnetic fields from the accretion disk, this configuration can generate powerful electric fields through induction. Much of this research was summarized in the book Black Holes: The Membrane Pardigm by Thorne, Price & MacDonald. 1986
Sunspot and active region processes. Some of these currents may initially be generated by the Pannekoek-Rosseland field.
All these mechanisms create the charge separations and currents using energy from other processes, usually gravity. The charge-separation itself is not the original energy process but can create non-thermal distributions of charged particles.
By the way, did you know that reputable scientists did research on cosmologies with net charge? I'll add that to my idea list for future blog posts.
I've collected a fairly extensive citation list for all these processes and plan to write more on them later. However, if I've missed any of the fundamental processes or other sites where we believe they operate, feel free to contact me by email or post a comment here. Comments will be favored if they include citations to the actual professional literature (no vanity journals!).
In one recent e-mail discussion, a correspondent claimed that EU advocates use all of these processes. However, aside from an indirect reference in Thornhill (2007) (Thornhill references a paper at mentions the Pannekoek-Rosseland field), I have found none. I would be interested to discover if EU advocates use such processes as the offset dipole or charge separation by radiation pressure. Considering how much of this early work was done by astronomers, it would suggest that the EU advocates knew they were making false statements when claiming astronomers ignore electric processes. Reports of citations in EU literature (title, author, and page number) which mentions any of the processes described above are welcome as well.
W. Thornhill. The Z-Pinch Morphology of Supernova 1987A and Electric Stars. IEEE Transactions on Plasma Science, 35:832–844, August 2007. doi: 10.1109/TPS.2007.895423