Coronal Expansion and Particle Propagation through the Planetary Space

This paper has been published as "Coronal Expansion and Solar Corpuscular Radiation," Planetary and Space Science, Vol. 12, pp. 451-461, 1964 (Pergamon Press). Significant information about the corpuscular radiation from the sun was deduced from studies of the aurora, magnetic storm phenomena, variation of intensity of galactic cosmic rays, etc. before satellite observations were available. In the \´40\´s and \´50\´s for example, it was established that the steady outward corpuscular flux, rather than radiation pressure, pushed the gaseous tails of comets away from the sun. From the direction of the tail and velocity of the comet, the velocity of the protons was qualitatively estimated. Direct measurements near the earth\´s orbit show a velocity of 300-600 km/sec and a density of 2-20 protons/cm3 . It now appears that the temperature of the sun is high enough so that an appreciable fraction of the protons escape from the gravitational field and continue travelling outward at supersonic velocities, ultimately being slowed down by collisions in interstellar space. Of great importance are the thermal conductivity of the corona and the electrical conductivity of the expanding plasma. Due to the latter condition, expansion of the solar corona pulls with it the general solar magnetic field, the magnetic lines are pulled out by the expanding plasma. Measurements of proton density, velocity and the sun\´s magnetic field as a function of solar activity give additional information on the source and behavior of the solar wind. (W.A.H.)