Challenges to common sense

Plasma is a different kind of animal. It doesn't behave as we expect it to and is found in unexpected places. Although plasmas exist in a wide range of conditions, all are composed of a percentage (often small) of charged particles—usually electrons and protons—mixed with neutral atoms or molecules.

This rich "soup" readily conducts electrical currents, especially in filaments that spiral along invisible magnetic-field lines. Their spiraling movement pinches single filaments tighter or draws neighboring filaments into a swirling, high-energy dance that often produces abundant electromagnetic radiation.

A notable characteristic of space plasma, revealed by satellites and space probes, is the tendency to form sharp boundaries between plasma with different properties. The resultant "cellular structure" can have profound astrophysical implications, such as generating electric fields in space and providing sources of energy for driving electric currents over very large distances.

A phenomenon called critical ionization velocity, first proposed by Nobel laureate Hannes Alfvén in his cosmogony theory, has been observed in both laboratory and space plasma. It implies, among other things, an exchange of momentum between ionized and neutral gases in the presence of magnetic fields. Yet another distinctive behavior discovered first in the near-Earth plasma is mechanisms that allow very efficient separation of different chemical elements or molecules.

Many of plasma's unique properties derive from the behavior of electrons. We easily forget that electrons are so unbelievably tiny that they respond to the faintest of magnetic and electrical fields. Being nearly 2,000 times lighter than protons, electrons are far more responsive to acceleration by electric fields. They travel much faster and even bunch together in interacting with the heavier, slower protons and other atomic nuclei that may be present in plasma. Electrons accelerated to high speeds yield the abundant radiation characteristic of plasmas in the laboratory and space.

The Sun's white light is a composite of hundreds of distinctive frequencies produced by atoms energized and ionized to differing degrees. Iron stripped of 12 electrons produce the ultraviolet light shown here.


Aurora Borealis (Northern Lights), the result on Earth of plasma ejected by the Sun interacting with the Earth's magnetic fields (top view of Earth looking down on the Arctic region). The same phenomena occurs in the Antarctic.


While space probes have yet to penetrate beyond the plasma sheath of the solar system, the heliosphere, considerable evidence points to the heliosphere's existence as a teardrop-shaped plasma body similar to Earth's magnetosphere. What lies beyond the heliosphere? Is the space there really empty, or will we find more plasma there? The plasma model asserts that we certainly will find plasma in the interstellar space, and even in the greater intergalactic space.

Such a view is contrary to the mainstream cosmological model, which holds that plasma should not be a pervasive presence in interstellar and intergalactic space—or even in interplanetary space. But plasmas are perversely different from what we expect. Let them be dispersed as they are in space, and our concepts of recombination temperatures, at which electrons and atomic nuclei or ions combine into neutral atoms, don't apply. Let the electrons be accelerated to extremely high speeds, as they are in the solar wind, and recombination concepts don't apply. Regardless of concepts and calculations, plasmas tend to persist in space. Furthermore, they still respond strongly to electromagnetic fields, even when their ionized fraction is much less than 1 percent.

Scientists driving the development of plasma models of the universe tend to be electrical engineers or plasma physicists, instead of astrophysicists and mathematicians who dominate cosmology today. For electrical engineers, plasmas are eminently practical. They already are in widespread use for industrial applications. They can be thoroughly studied experimentally, and they exhibit similar behaviors over a wide range of size scales. Thus the equations for controlling a plasma stream etching a silicon chip that will become a computer microprocessor are basically the same equations that govern the movement of the aurora or solar wind, or, they say, a galaxy.

With apparent inevitability, an increasing number of electrical engineers have extended their plasma interests beyond Earth, into such realms as interplanetary "space weather" and plasma laboratory astrophysics. Their fundamental view on cosmology is that electromagnetic forces sculpt the broad outlines of the universe; gravitational forces shape the details only after electromagnetic forces have first drawn the diffuse matter close enough together for gravity to become significant.

The plasma modelers readily admit that they offer no proposal about the universe's origin and age. That issue, as well as the size of the universe, lies beyond their horizons of experimentation and simulation. Nonetheless, at the beginning of the twenty first century, electrical engineers are marshaling a growing body of evidence that points to the necessity of integrating plasmas into the core of cosmological thinking.

At the same time, mainstream cosmology is not about to welcome the plasma model. Cosmology of the twentieth century remains dominated by gravitation modeling, based especially on Albert Einstein's general relativity theory. Although cosmologists tried at the beginning of the century to include electromagnetic forces in their calculations, the equations proved too complicated to handle, and, in any case, the gravity dominated models became extremely popular to the lay-person. Thus today in cosmology, gravity rules, and its progeny, the big bang model, is widely accepted as providing the "true" explanation of the nature of the universe.