Credits: UPPER: John Dyer;NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL); CFA, TRACE Team, NASA.
MIDDLE: J. Trauger (JPL), NASA; NASA, ESA and the Hubble Heritage Team;J. A. Biretta et al., Hubble Heritage Team (STScI /AURA), NASA
LOWER: P. Stomski (W. M. Keck Observatory), Caltech, U. California

CAPTION: UPPER: high-voltage filaments-electrical discharge in a plasma lab; lightning-electrical
discharges in Earth's atmosphere; solar filaments-electrical discharges in the Sun's atmosphere.
MIDDLE: Saturn's auroras-electrical discharges around Saturn's magnetic poles; ant nebula-electrical
discharges along a star's magnetic axis; galactic jet-electrical discharges from an active galactic nucleus.
LOWER: observatory-a facility astronomers employ to avoid seeing electrical discharge in space.

Jun 27, 2005
Seeing Electricity in Space

We tend to perceive only what’s familiar. So when new discoveries open up unfamiliar worlds, they present us with a dilemma. To see new worlds accurately may require a radical step—the suspension of prior beliefs.

Let’s start with what’s familiar.

Prior ideas, experiences and memories form the foundation of our thinking. They make up the “what’s familiar”. “What’s familiar” is things we bump into and think of as solid, other things we splash in and think of as liquid, a few things we feel blowing past us and think of as gas. “What’s familiar” is thinking of these things as made up of atoms, atoms that have mass, atoms that have positively charged particles on the inside and negatively charged particles on the outside, atoms that can gain and lose these particles but that have few electrical effects. “What’s familiar” is the accumulation of our thinking and acting and remembering as creatures who live on the surface of a wet, rocky body called Earth.

But there are things and events above the surface and below the surface—even on the surface—that we have not thought about or remembered. Not long ago our ancestors thought differently about things and remembered events differently. What was familiar for them was not thinking in terms of solids, liquids and gases but thinking in terms of earth, water, air and fire. And if what’s familiar has changed before, it can change again.

For some time now we’ve been accumulating unfamiliar experiencesabove the surface. Early in the twentieth century we began to discover atoms that are unfamiliar because they are missing one or more negatively charged particles. The remaining portions of these atoms are positively charged. The presence of these negatively and positively charged particles is the distinguishing characteristic of what we now call plasma. In the second half of the twentieth century we discovered that plasma fills the space between planets and stars.

Plasma behaves in unfamiliar ways. But our habits of perception can make it difficult to see plasma as something completely different from a gas. Its similarities to a gas are overshadowed by the dissimilarities. And if we can break free from prior ideas about gases, we make the unfamiliar ways of plasma familiar. And we can see a new universe.

A charged particle that moves is an electric current. This is a familiar thought when we’re doing electrical things, but we’ve not thought about it when we’re doing things in space. An electrical current is accompanied by a magnetic field that wraps around the current and gets weaker with distance from the current. With more charged particles moving in the same direction, and with moving faster, the magnetic field gets stronger. Again, this is a familiar thought when we’re doing electrical things. But when astronomers discovered magnetic fields in space, they were surprised and mystified about how to explain them. They tried to conjure magnetism out of gravity and mass.

Because the charged particles are moving through this magnetic field that gets stronger toward the axis of movement, particles that are not moving exactly along that axis are squeezed toward the axis. Plasma scientists call this the “pinch effect”. Outlying charged particles, together with the neutral atoms they bump into, are pulled into the current channel. Outlying areas are depleted and the channel gets denser. It self-constricts until the gas pressure on the inside balances the magnetic pressure on the outside. This balance of pressures along the axis produces long, thin filaments of matter that are sharply separated from their rarified environments.

We remember that this is what happens in a lightning stroke (or at least this is how we think about what happens in a lightning stroke), and it seems familiar: We understand. But we had not thought about this happening in space.

Kristian Birkeland thought this might be what happens in the aurora. He trekked to the Arctic Circle to measure the magnetic fields from the constricted channels that made up the auroral currents. (These “Birkeland currents” were later named after him.) He speculated that this might be what happens in the filaments that make up solar prominences and the solar corona. He thought the filaments might carry electric currents from the Sun to Earth.

Such ideas were too unfamiliar for astronomers conditioned to think in terms of gravity and mass. They clung to their familiar ideas of mass particles until artificial satellites orbited through and measured the electrical filaments that were the auroral currents. Even then, the idea was too unfamiliar for them to recognize that the moving charged particles from the Sun were also currents.

Because gravity-oriented astronomers are familiar with moving masses, they seldom think about charges. What’s not familiar, what has no conceptual framework for understanding, is often not even perceived. So they think of moving charged particles from the Sun as a “wind” instead of an electric current. They think of charged particles falling on a planet or on a moon as a “rain” instead of an electrical discharge. They think of charged particles moving along a magnetic field as a “jet” instead of a field-aligned power cable. They think of abrupt changes in the density and speed of charged particles as a “shock front” instead of a double layer that can dissipate electrical energy and even explode.

They can’t see the electrical-particle forest for the mass-particle trees. They are lost in a plasma universe, seeing charged particles in motion but thinking in terms of gas kinetics and gravity.

Plasma cosmologists think differently. They remember their experience with currents in a laboratory. They are familiar with the “right-hand rule”: When they point the thumb of their right hand in the direction of the current, their fingers will curl in the direction of the magnetic field. In the space between two parallel currents, the two magnetic fields will have opposite directions. Because north and south poles attract each other, the two currents will move toward each other. But as they get closer, the electrical repulsion between them will become stronger than the magnetic attraction. The two currents will begin to twist around each other. (See Thunderbolts of the Gods, Chapter One, page 24.)

Plasma cosmologists recognize these twisting filaments in the penumbrasof sunspots and in coronal streamers. Space probes have detected them in a plasma tail from Venus that is identical to the ion tails of comets. The glowing filaments in so-called planetary nebulas and in misnamed “supernova remnants” are familiar. The jets from Herbig-Haro stars and from active galaxies are familiar.

Once electric currents in space have become familiar, once they are understood, they can be perceived almost everywhere. The only place they are missing is in modern astronomical theories.

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

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