A study of magnetic storms and auroras

New notations for magnetic disturbance fields are proposed, based on the theoretical consideration of the electric current systems by which they are produced. A typical magnetic storm begins suddenly when the onrush of the front of the solar gas is halted by the earth's magnetic field. This effect (DCF field) is most markedly observed as a sudden increase of the horizontal component of the earth's field (the storm sudden commencement, abbreviated to ssc)— like a step function. In many cases, however, the change of the field during the ssc is more complicated, and different at different places. Such a complexity superposed on the simple increase (DCF) is ascribed to a complicated current system generated in the polar ionosphere (DP current). It is found that the changes of electromagnetic conditions in the polar regions are communicated, without delay, to lower latitudes, even down to the equatorial regions. It is inferred that the equatorial jet is affected by such a change and produces the abnormal enhancement of ssc along the magnetic dip equator. From the extensive analysis of several magnetic storms that occurred during the IGY and IGC, it is suggested that the capture of the solar particles in the outer geomagnetic field occurs when irregularities (containing tangled magnetic fields and high energy protons) embedded in the solar stream, impinge on the earth.. Thus the development of a magnetic storm depends on the distribution of such irregularities in the stream. The motions and resulting currents and magnetic fields of such "trapped" solar particles are studied in detail for a special model. It is inferred that a large decrease (DR field) must follow the initial increase; it is ascribed to the ring current produced by such motion of solar protons oi energy of order 500 Kev. It is proposed that during the storm there appears a transient 'storm-time1 belt well outside the outer radiation belt. It is predicted that the earth's magnetic field is reversed in limited regions when the ring current is appreciably enhanced. This involves the formation of neutral lines there. These may be of two kinds, called X lines or 0 lines according as they are crossed or encircled by magnetic lines of force. These may be entirely separated or may be joined to form a loop, called an OX loop. It is shown that one of them, the X line, which is connected with the auroral ionosphere by the lines of force, could be the proximate source of th