The Ultraviolet Light Theory of Aurorae and Magnetic Storms. Continued

The ultraviolet light theory of aurorae and magnetic storms, Phys. Rev. 33, 412 (1929), 34, 344 (1929), did not agree with all the facts. Making use of the further development of the theory of the outer atmosphere, Phys. Rev. 34, 1167 (1929), 35, 240 (1930), the discrepancies in the ultraviolet theory are removed with no change in the original assumptions. The first phase of the average world-wide magnetic storm is attributed to the sudden increase in the eastward ion drift current which gridles the earth caused by an increase in the long free path ions produced by a solar ultraviolet flare. The second phase of the storm comes about from the heating of the high atmosphere by the flare. The atmosphere expands and the outward movement of the ionized regions across the earth's magnetic field gives rise to a westward current in the high atmosphere flowing around the earth. The movement also decreases the long free path ions and increases the short free path ions; this prolongs the westward current.Assuming that the earth has no excess charge the high flying ions distilled from low latitudes fall into the top of the atmosphere of the auroral latitudes in maximum numbers at about 1 P.M. It takes them until about 6 P.M. to fall by diffusion and electrical drifts down to the short free path levels at 100 km. They set up a system of electrical currents in the high atmosphere wheeling in a rather distorted course around a focus at about 6 P.M. in latitude 60^∘{} to 70^∘{}, one system in the arctic and one in the antarctic. The current systems give rise to the diurnal variations of the average world-wide magnetic storm. If the earth has a resultant charge in excess of about 50 coulombs the present theory would probably be untenable, or would require extensive modification.The lower limits of the long and short free path ion banks of the polar atmosphere agree, respectively, with the observed lower boundaries of the streamers and the structureless luminosity of the aurora.