IF I SEEK US
Cosmology - General
Plasma: The other 99.9%
How do you see the Solar System? The simple view is gas giants and rocky asteroids and planets moving through nearly empty space. The sophisticated view illustrated above, shows the heliospheric current sheet, a component of the interplanetary plasma we call the Solar Wind, awash throughout the Solar System.
Over 99.9% of the universe is made of plasma, including the Sun
all stars, and most of the space in between. So if you don't know
basic properties of plasmas, then you might not understand the
properties of most of the universe.
1. Plasmas are formed by adding energy to gas, causing it to
ionize (an atom looses one or more electrons). For example, if
hydrogen ionizes, it produces equal numbers of negatively charged
electrons and positive ions (in this case, protons). Even a one
2. Plasmas are affected by electromagnetic forces 1039 times
greater than the force of gravity. So strong is its influence that
creates the ballerina's skirt shaped heliospheric current sheet (see
diagram), the largest structure in the Solar System, extending out
3. Plasma is not always electrically neutral. In general it is quasi-neutral, meaning that localized regions of charge separation may occur. And objects that comes into contact with a plasma will charge negatively, such as dust, spacecraft and the surface of the Moon.
4. Plasma is a better conductor of electricity than copper. Its conductivity and response to electromagnetic influences distinguishes it from a gas. Indeed, metals can be classified as plasma, too, because they contain free electrons.5. Moving plasma can self-generate electromagnetic fields.
6. Plasma can store energy in magnetic fields.
7. Plasmas form double layers between regions of
different densities, temperatures or magnetic field strengths. A
8. Relative movement of different plasma regions produces electric currents within them.
9. Electric current in plasma produces "pinched" filaments known as Birkeland currents. Birkeland currents form the cosmic power lines and the "wires" of cosmic circuits. An example is found in the ionosphere where these filaments carry up to a million amps, and power the aurora. Those in the Sun's prominences have been estimated to carry up to 100 billion amps (1011 A).
10. Birkeland currents collimate "jets" of matter and charged particles. Astronomical "jets" were so named by astrophysicists because they look somewhat like fluid jets produced in the laboratory. Yet astronomical jets look nothing like a supersonic jet coming out of a nozzle, with all the attendant fluid instabilities. Heated gas should quickly disperse in space but the magnetic pinch of a Birkeland current can maintain filaments of glowing matter over thousands of light years.
11. Synchrotron radiation from pinched current filaments can be in the form of x-rays and gamma rays.
12. The pinch effect can be used in nuclear fusion reactors.
13. Plasma phenomena scale in size over at least 14 orders of magnitude. So the same phenomena may be seen in a dense laboratory plasma and a tenuous space plasma.
14. Parallel plasma filaments attract one another with a force inversely proportional to their distance apart. Compare this with gravity, which attracts matter with a force inversely proportional to the SQUARE of the distance. That makes pinched Birkeland currents by far the most effective way of condensing rarefied dust and gas to form molecular clouds and stars.
So since the Universe is 99.9% plasma, the important question is not IF the properties of plasma are important in cosmology, but HOW come we focus on the puny force of gravity?...............................
"The space data from astronomical telescopes should be treated by scientists who are familiar with laboratory and magnetospheric physics, circuit theory, and of course modern plasma physics." Hannes Alfvén, Double Layers and Circuits in Astrophysics, IEEE Transactions on Plasma Science, Vol. PS-14, No. 6, December 1986.
Contributed by Ian Tresman