Soft Radiation Events at High Altitude during the Magnetic Storm of August 29-30, 1957

During a balloon flight made from Fort Churchill on August 29, 1957, showers of x-rays were encountered at an atmospheric depth of about 11 g ${\mathrm{cm}}^{-2\mathrm{}}$. At times their flux was as high as 20 photons ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{sterad}}^{-1\mathrm{}}$. The close connection between the appearance of these x-rays in the 100-kev energy region and storm-type decreases in the local geomagnetic field is shown. The one observation that bears on the point is consistent with these x-rays being produced by electron bremsstrahlung in the terrestrial atmosphere. There are features of the x-ray behavior which show that the primary electrons must be local in character quite apart from geomagnetic cutoff considerations. By "local" is meant that the electrons either acquire the main part of their kinetic energy in the neighborhood of the earth or that they are accelerated at the sun, are trapped in magnetic clouds, and drift to the earth where they are released. It is suggested that acceleration of electrons is a rather general characteristic of the region surrounding the earth and that their association with aurorae and geomagnetic storms may be special features.