Theory of the Aurora Based on Magnetic Self-Focusing of Solar Ion Streams

Abstract

It is assumed that the sun emits a jet of an electrically neutral mixture of fast electrons and positive ions, and that the space between the sun and earth is filled with an ionized, electrically neutral gas. As the jet proceeds the fast electrons are slowed down and scattered by encounters with the space ionization, being continually replaced by slow electrons from space. The stream of positive ions continues as an electric current, but at all times the stream and surrounding gas are closely electrically neutral. Due to the magnetic field of the electric current, the fast moving positive ions are continually compressed into the stream and the fast electrons and slower ions are ejected from the stream. This is "magnetic self-focusing." The stream develops into a narrow core which if correctly aimed enters the earth's magnetic field and is diverted to auroral zones according to the calculations of Störmer. Meinel's observations indicate that the primary solar particles in the stream are mainly protons of speed greater than 3×${10}^8$ cm ${\sec }^{-1\mathrm{}}$. A speed of order of ${10}^{10}$ cm ${\sec }^{-1\mathrm{}}$ of the protons is required for correct Störmer orbits into auroral latitudes and penetration to 60- to 80-km levels in the upper atmosphere. For a stream which carries sufficient energy for an aurora, the density of space ionization between the sun and earth is calculated to be at least ${10}^{-5\mathrm{}}$ electron ion pairs ${\mathrm{cm}}^{-3\mathrm{}}$ to support magnetic self-focusing and not more than ${10}^9$ pairs ${\mathrm{cm}}^{-3\mathrm{}}$ for the fast protons to be able to reach the earth. It is suggested that the auroral rays are not the solar proton stream but are formed when the protons are stopped in the upper atmosphere. Due to the charges and absorbed energy of the protons, oxygen and nitrogen particles of the atmosphere are ejected outward to great heights along the lines of magnetic force and form the auroral rays and streamers.