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 Stormer. Meinel's observations indicate that the primary solar particles in the stream are mainly protons of speed greater than 3X10 8 cm sec -1 . A speed of order of 10 10 cm sec -1 of the protons is required for correct Stormer 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 electron ion pairs cm"" 3 to support magnetic self-focusing and not more than 10 9 pairs cm -3 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.

Geomagnetic storms, auroras and associated effects

“…It is necessary that the cloud is almost exactly electrically neutral. The concept of a stream of highly charged plasma (that is, an electric current) emanating from the Sun, has recently been revived by BENNETT et al (1954), but has been criticized by Ferraro and appears unacceptable.…”

Solar-terrestrial time delays

“…If the sun has a dipole magnetic moment M apart from the random multipolar fields that are observed on its surface [3], the resulting field will deflect a proton beam in its passage out to the earth. The word "beam" is used in view of the self-focusing action that can be expected in a current of fast protons [2]. S'mce the neutralizing electrons come from the interplanetary matter, they will follow *This work was assisted by the joint program of the U.S. Office of Naval Research and the U.S. Atomic Energy Commission.…”

“…If the latter are caused by ion streams originating in the sun, as is generally believed, then this time lag implies stream velocities of about 1.5 X !0 8 cm sec -•. However, convincing evidence [2] has been presented in favor of the hypothesis that the streams actually consist of fast (i0 TM cm sec -•) protons accompanied by slow electrons to provide electrical neutrality. In this event, the time lags must be accounted for on some basis other than tr•vel time.…”

56. Some effects which can accompany magnetic storms

“…If the plasma moves through some other plasma, retardation of the electrons is much more strong than the retardation of protons. This was indicated by W. Bennet and E. Hulburt [6], who suggested that the stream must consist of highvelocity protons and slow electrons. However, such combination of different velocities represents an electrical current, the increase of which from zero being restricted by self-induction.…”

“…If i/=o-2, the concentration TZ« io 6 , T&6 x io 6 degrees. The linear dimensions are reduced considerably and probably constitute some tens of kilometers.…”