Thursday, February 16, 2012

365 Days of Astronomy: The Electric Universe

I recently completed an entry for the 365 Days of Astronomy podcast, “The Electric Universe”.  This podcast is an expansion on my post “The REAL Electric Universe”.

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.

Breaking Wind?
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)
These ideas have a fascinating history that I am still exploring, and some aspects of the science are still not fully resolved.

But that is a topic for another time...

Just Some of the References Behind the Podcast
    •    S. Rosseland. Electrical state of a star. Monthly Notices of the Royal Astronomical Society, 84:720–728, June 1924.
    •    A. Pannekoek. Ionization in stellar atmospheres (Errata: 2 24). Bulletin of the Astronomical Institutes of the Netherlands, 1:107–118, July 1922. 
    •    R. Wildt. Note on stellar ionization and electric fields. Monthly Notices of the Royal Astronomical Society, 97:225–231, January 1937. 
    •    W. F. Swann. Acquirement of Cosmic-Ray Energies by Electromagnetic Induction in Galaxies. Physical Review, 96:240–241, October 1954. doi: 10.1103/PhysRev.96.240.
    •    J. Bally and E. R. Harrison. The electrically polarized universe. Astrophysical Journal, 220:743–744, March 1978. doi: 10.1086/155961. 
    •    C. Alcock. The surface chemistry of stars. III - The electric field of a chemically inhomogeneous star. Astrophysical Journal, 242:710–722, December 1980. 10.1086/158506. 
    •    E. R. Wollman. Substantial equilibrium charge separation in a self-gravitating plasma, with application to galaxies. Physical Review A, 37:3052–3057, April 1988. doi: 10.1103/PhysRevA.37.3052. 
    •    H. Fichtner and H. J. Fahr. Towards a rigorous model for multifluid expansions of stellar coronae - Application to the solar wind. Astronomy & Astrophysics, 241:187–196, January 1991. 
    •    J. D. Scudder. Why all stars should possess circumstellar temperature inversions. Astrophysical Journal, 398:319–349, October 1992. doi: 10.1086/171859. 
    •    L. Neslušan. On the global electrostatic charge of stars. Astronomy & Astrophysics, 372:913–915, June 2001. 10.1051/0004-6361:20010533. 
    •    B. P. Pandey, J. Vranješ, P. K. Shukla, and S. Poedts. Equilibrium Properties of a Gravitating Dusty Plasma. Physica Scripta, 66:269–272, 2002. 10.1238/Physica.Regular.066a00269. 
    •    L. I. Schiff. A Question in General Relativity. Proceedings of the National Academy of Sciences, 25: 391–395, July 1939. 
    •    L. Davis. Stellar Electromagnetic Fields. Physical Review, 72:632–633, October 1947. doi: 10.1103/Phys- Rev.72.632. 
    •    E. W. Hones, Jr. and J. E. Bergeson. Electric Field Generated by a Rotating Magnetized Sphere. Journal of Geophysical Research, 70:4951–4958, October 1965. 
    •    David Webster & Robert Whitten. Which Electromagnetic Equations Apply in Rotating Coordinates?  Astrophysics and Space Science, Volume 24, Issue 2, pp.323-333
    •    L. Z. Fang. On the surface states sustained by the electric field of rotating neutron stars. Monthly Notices of the Royal Astronomical Society, 193:107–110, October 1980. 
    •    F. C. Michel. Relativistic charge-separated winds. Astrophysical Journal, 284:384–388, September 1984. 10.1086/162417. 
    •    P. L. Rothwell. The superposition of rotating and stationary magnetic sources: Implications for the auroral region. Physics of Plasmas, 10:2971–2977, July 2003. 10.1063/1.1582473. 
    •    S. Cuperman and A. Harten. The Radial Electric Field in the Solar Wind. Astrophysical Journal, 169: 165–169, October 1971. doi: 10.1086/151127. 
    •    L. Maraschi, C. Reina, and A. Treves. On Spherical Accretion near the Eddington Luminosity. Astronomy & Astrophysics, 35:389, October 1974. 
    •    G. Michaud and G. Fontaine. Electric fields, accretion, and stellar winds in helium-rich atmospheres. Astrophysical Journal, 229:694–699, April 1979. doi: 10.1086/157004. 
    •    I. Zouganelis, N. Meyer-Vernet, S. Landi, M. Maksimovic, and F. Pantellini. Acceleration of Weakly Collisional Solar-Type Winds. Astrophysical Journal Letters, 626:L117–L120, June 2005. doi: 10.1086/431904. 
    •    N. Meyer-Vernet. How does the solar wind blow? A simple kinetic model. European Journal of Physics, 20: 167–176, May 1999. doi: 10.1088/0143-0807/20/3/006. 
    •    L Zampieri, R. Turolla, L. Foschini and  A. Treves.  Radiative Acceleration and Transient, Radiation-induced Electric Fields.  Astrophysical Journal, 592: 368-377. 
    •    McBreen, B.; Winston, E.; McBreen, S.; Hanlon, L.  Gamma-ray bursts and other sources of giant lightning discharges in protoplanetary systems.  Astronomy and Astrophysics, v.429, p.L41-L45 (2005)
    •    R. D. Blandford. Accretion disc electrodynamics - A model for double radio sources. Monthly Notices of the Royal Astronomical Society, 176:465–481, September 1976. 
    •    R. V. E. Lovelace. Dynamo model of double radio sources. Nature, 262:649–652, August 1976. 10.1038/262649a0. 
    •    K. S. Thorne, R. H. Price, and D. A. MacDonald. Black holes: The membrane paradigm. 1986.
    •    P. P. Kronberg, R. V. E. Lovelace, G. Lapenta, and S. A. Colgate. Measurement of the Electric Current in a Kpc-Scale Jet. ArXiv e-prints, June 2011. 
    •    G. E. Hale and H. D. Babcock. An attempt to measure the free electricity in the sun’s atmosphere. Proceedings of the National Academy of Sciences, 1(3):123–127, March 1915.
    •    P. Foukal and S. Hinata. Electric fields in the solar atmosphere - A review. Solar Physics, 132:307–334, April 1991. doi: 10.1007/BF00152291. 


Jeff said...

W.T."Tom" Bridgman said...

To Jeff,
You missed an important point in your comment.

Electric fields are difficult to detect, but electric CURRENTS are not, as they are strong synchrotron emitters. Plasma physicists no longer talk about 'dark currents' because we know they are not so dark - they do emit in radio wavelengths. That is what we would detect. Other things (like thermal differences in a plasma) can generate a charge separation which can create an electric field.

EU's biggest problem is that application of even basic electromagnetism demonstrates that claims such as the electric sun or Peratt's galaxy-powering currents don't match the observations.

gregster said...

"EU's biggest problem is that application of even basic electromagnetism demonstrates that claims such as the electric sun or Peratt's galaxy-powering currents don't match the observations."

Why is the Sun's temperature so much higher at the Sun's surface?

W.T."Tom" Bridgman said...

To gregster,

Which 'temperature' do you mean? When they describe this region with a 'temperature' it is a reference to the *formation* temperature of the ion *assuming thermal equilibrium*, which the transtion region is not. Physics uses the term 'temperature' in many different ways. Do you know what a brightness temperature or effective temperature is?

Boiling water and the steam immediately above it are at the same temperature, yet you can put your hand in the steam without burning, but not the water. Why?

You also failed to note in the reference list above that there are a lot of solar and stellar physicsists looking at electric fields in stars. If all the problem took was an electric field, it would be solved by now.

BTW, where is the EU corona predictions that produce NUMBERS that we can compare to actual MEASUREMENTS.

Also, we still haven't found the current powering your electric star, or the battery, or are you supporting perpetual motion?