Propagation of solar cosmic rays through interplanetary magnetic field

Abstract

In recent years evidence has been accumulating that low-energy solar cosmic-ray particles arrive at the earth after intense solar disturbances. The time-delay of polar-cap absorptions and of geomagnetic storms, which follow after an intense solar radio outburst of type IV, indicates that solar cosmic-ray particles originating to the west of the solar central meridian reach the earth earlier and more easily than those from the east. The model of the interplanetary magnetic field, which may be appropriate for the explanation of this evidence, is as follows: The interplanetary magnetic field is formed by the outward-streaming solar winds which carry the imbedded solar magnetic fields and the lines of force also linked with the sun itself. The rotation of the sun produces a curvature of streams and consequently of the lines of force, which are convex toward the west. Since the injected solar particles will tend to travel along the existing magnetic lines of force, this model explains the western excess of the arrival of solar cosmic rays as well as the inequality of their travel time with respect to the heliographic position. The estimated intensity of the magnetic field is of the order of 10−3 to 10−5 gauss near the earth's orbit.