But even this extended content did not cover all the items I would have liked to include, so I'll add a few notes, caveats, and qualifiers here.
Nature Rarely Accommodates the Pure Form
Think of how difficult is was for Isaac Newton to derive the pure form of F=ma, in a world surrounded by frictional forces. Similarly, one of the problems we run into is that phenomena such as the Pannekoek-Rosseland (P-R) field and the field of an offset rotating magnetic dipole are next to impossible to obtain in a 'pure' form in nature.
For the P-R field, any deviation from spherical symmetry will create a non-radial component to the electric field. This deviation from symmetry will start charges moving (a current) which will generate a magnetic field, which makes the motion even more complex. This complex set of motions may find a near-equilibrium configuration with the rest of the star's structure, perhaps initializing the star's magnetic dynamo and other plasma motions near the star's surface.
For the case of the rotating dipole, the configuration described in the podcast generates an electric field in a vacuum. But in reality, pulsars, stars, and even planets, are surrounded by a plasma. If an electric field is created by the dipole rotation in this environment, the charges in the plasma will start moving, distributing themselves in a configuration that tries to cancel the electric field. But the inertia of the particles will allow them to overshoot strict electrical neutrality, much the way it occurs in Langmuir's plasma oscillations (wikipedia). In configurations like pulsars, stars and planets, additional complexities are created by winds of charged particles, either streaming off the atmosphere of the pulsar or planet, or off a nearby star. The combination of all these complex process makes magnetospheric physics (wikipedia) one of the most complex fields of study in the space sciences.
And the last qualifier I'll add is for the description of stellar winds driven by radiation pressure. While the bulk of the stellar wind is electrons and protons, they are virtually invisible to distant spectrographs as they have no well-defined spectral lines. Modern kinetic treatments of the solar wind include electric fields which can be created by regions of charged particle separation in the wind. But since the electric field is determined by the particle distribution, and it's easier to measure the particle distribution, the electric field is usually just a bookkeeping tool for tracking the forces in the flow.
In addition, elements heavier than helium in the stellar wind are more readily detected by remote sensing techniques since they have complex spectra. The energy-levels of these atoms interact with the photons streaming out from the star, which applies a net force on the atoms. For distant stars, we can detect these winds powered by the absorption and re-emission of the atoms.
Even More Goodies...
And there are some other processes which I did not have time to discuss in the podcast, but which are possible topics of future interest.
- Ambipolar diffusion of solar wind plasma around structures, as well as photoelectric ionization on the Moon and asteroid surfaces can generate potentials of several hundred volts. These voltages can impact the safety of astronauts as well as satellites and other equipment. Evidence for Acceleration of Lunar Ions (1972)
- In 1966, Fred Whipple (of the snowball comet theory) suggested that lightning in the dust-filled solar nebula might be responsible for the formation of chondrules in meteorites. Chondrules: Suggestion Concerning the Origin (1966)
But that is a topic for another time...
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