Measurements of the electron content of the interplanetary medium between Earth and Venus

Abstract

Observations of the relative propagation time of radar pulses to Venus for two frequencies, 40 MHz and 430 MHz, give the columnar electron content between the radar site and the surface of the planet. An independent measurement of the electron content of the earth's ionosphere allows us to obtain the electron content of the interplanetary medium. Assuming an inverse square law for the electron concentration between the orbits of Venus and earth we obtain electron concentrations at 1 AU ranging from 0.9 el cm−3 to 8.8 el cm−3 with an average over the thirteen days' observations of 4.5 el cm−3.