Planetary Nebulae

A plasma is a highly ionized gas in which the number of free electrons is approximately equal to the number of positive ions. Sometimes described as the fourth state of matter, plasmas occur in interstellar space, in the atmospheres of stars, in discharge tubes, and in experimental thermonuclear reactors. Plasma behaves differently from that of a gas. They can be created in the laboratory by supplying energy to a low-pressure gas until the mean kinetic energy of its constituent atoms and molecules is comparable to the ionization potential of the atoms or molecules. At very high temperatures, exceeding 50,000 Kelvin, collisions between gas particles cause a cascading ionization process. In discharge tubes, such as fluorescent lamps, the temperature remains quite low due to the atoms and molecules imparting their energies to the walls of the chamber, causing cooling and recombination. – Oxford Dictionary of Science.

Electro-magnetism, vastly more powerful than gravity, are the dominant forces at play in plasma fields, such as those found in the laboratory and in space. The flow of currents through a plasma is influenced by magnetic fields and it is these magnetic fields that shape planetary nebulae. Plasma exhibits an intricately complex structure and morphology that sets it apart from the behavior of neutral gases. Plasma tends to manifest itself in the form of cells and filamentary structures of differing electrical characteristics by the way it interacts with the magnetic fields. Electrical filaments are like vast transmission lines with virtually no limit to the distance over which they can operate. These filaments, tend to braid themselves into ropes that attract each other over long distances and repel each other at short distances.

plasma-filaments2

The aurora are currents of charged particles twisting and spiraling through the ionosphere. The electrical currents of the aurora are named after the Norwegian scientist, Kristian Birkeland. In 1908, he suggested that auroras may originate as a secondary effect of plasma emissions ejected from the Sun. He proposed that polar electric currents spiralling down into the ionosphere flow along the geomagnetic field lines. His theory of field aligned currents originating from the sun was dismissed by most scientists and after being dismissed for years, his theory was finally verified when the U.S. Navy satellite, 1963-38C, was sent into space in 1963. It was equipped with a magnetometer which measured the strength and direction of the magnetic fields in the ionosphere. The currents were later named “Birkeland currents” in his honour.

Birkeland-aurora

To be continued…..

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