home • about • essential guide • picture of the day • thunderblogs • news • multimedia • predictions • products • get involved • contact

picture of the day             archive             subject index          


Credit: Copyright 2005 Blaise Fraser, used with permission
 

Sep 27, 2007
Electric Currents Big and Small

The novelty plasma ball demonstrates many of the properties of plasma that can be seen in the Sun, in nebulae, and in galaxies.

Blaise Frazier's beautiful photo of the spherical electrode in the centre of a plasma ball shows a blue filamentary streamer as it wavers during the 8-second exposure. Thousands of volts of electricity ionize the gas in the globe, ripping electrons from molecules and atoms. As electrons recombine with the ions, the gas gives off light. The colors depend on the kind of gas filling the globe.

The plasma ball illustrates some of the fundamental characteristics of plasma. The blue streamer looks flat, but that is an illusion of the photography. In reality, the filament is as thin as the light blue edges. It flickers between the two sides and extends from the electrode in a thin tube to the outer glass sphere of the ball.

Sometimes called a plasma cable, or plasma rope, the filament is the result of electrons and ions flowing through the plasma (i.e., an electric current). The current generates a magnetic field that surrounds the filament like hoops around a beer barrel. The magnetic field pinches the current and keeps it collimated (or wire-like).

When we take off a nylon sweater in a dark room and we see tiny sparks fly, we are seeing similar but smaller filamentary discharges. We see larger filamentary discharges as lightning in storms. The flares we see erupting from our Sun are even larger filaments. Because of the greater distances involved and the different magnetic fields and particle densities, flares appear to move in slow motion. And finally, filaments the size of solar systems make up nebulae.

Although non-neutral plasmas can be created in the laboratory, space plasmas generally contain equal numbers of negatively charged electrons and positively charged ions. They are considered to be electrically neutral. And since plasmas are also as electrically conductive as a lightning rod, this suggests that if a charge build-up should occur, then it would be neutralised quickly. But this view, like that of the “flat” filament in the plasma ball, is an illusion.

In 1831, Michael Faraday invented the homopolar motor/generator (also called a Faraday disk). It consists of a conducting disk in an axial magnetic field. The disk may be rotated in the magnetic field to generate an electric current between its axis and its edge. Or electric current may be passed from axis to edge to cause the disk to rotate in the magnetic field. In that way, the conducting atmosphere of the Sun is caused to rotate faster at the equator than at higher latitudes, when we should expect the expulsion of the solar wind to slow it.

Hannes Alfvén described the circuit for this Faraday motor many decades ago, but he didn’t consider its link with a greater galactic circuit. The current "disk" of the Sun is the heliospheric current sheet that flows between the Sun and the outer reaches of our solar system. And the axial circuit consists of Birkeland currents flowing along the "open" polar magnetic field lines.

Similarly, the galactic disk is the disk of a Faraday motor, caused to rotate by Birkeland currents flowing along the axis and out along the spiral arms. Stars in the spiral arms receive their power from those galactic currents. Galaxies, in turn, are threaded like "Catherine wheels" on intergalactic Birkeland currents. The cosmic circuitry of Birkeland currents can be traced by their magnetic fields.

So, far from being electrically sterile, cosmic plasma is awash with electric current filaments. And just like Frazier's plasma ball, we see the same beauty and evidence of currents in astronomical nebulae, glowing hydrogen HII regions, and planetary auroras.
We live in an Electric Universe!
___________________________________________________________________________

Please visit our Forum

The Electric Sky and The Electric Universe available now!

  EXECUTIVE EDITORS: David Talbott, Wallace Thornhill
     MANAGING EDITORS: Steve Smith, Mel Acheson
  CONTRIBUTING EDITORS: Michael Armstrong, Dwardu Cardona,
Ev Cochrane, C.J. Ransom, Don Scott, Rens van der Sluijs, Ian Tresman
  WEBMASTER: Brian Talbott

Copyright 2007: thunderbolts.info

home  •  thunderblogs  •   forum  •  picture of the day  •   resources  •  team  •  updates  •  contact us