Low-Energy X-Rays from Interplanetary Space

Abstract

IT is generally believed that the Sun is a source of highly ionized gas which streams outward through the solar system at all times and in all directions¹. At the orbit of the Earth, even under the quietest solar conditions, the velocity and density appear to be of the order of 500 km./sec. and 10² to 10³ particles/cm.³ respectively. (When the Sun is very active velocities greater than 1,500 km./sec. and densities up to 10⁵ cm.³ may be produced sporadically.) Theoretically², it is expected that this steady gas stream will finally become unstable at some radial distance from the Sun and establish a region of highly disordered interplanetary magnetic field and plasma.