The diffraction of galactic radio waves as a method of investigating the irregular structure of the ionosphere

Abstract The amplitudes of the radio waves received from a radio star at two points separated by about 1 km have been studied and compared. The results indicate that the variations of phase and amplitude at one point can be ascribed to the steady drift of an irregular wavepattern over the ground. It is shown how the structure and movement of the wave-pattern can be deduced from the observations. The irregular wave-pattern across the ground can be thought of as a diffraction pattern produced by the passage of the waves through a portion of the ionosphere which imposes irregular changes of phase on it, and it is shown how the ionospheric characteristics can be deduced. The ionospheric irregularities are shown to have a lateral extent of the order 2 to 10 km, and a variation of electron content of about 5 × 109 electrons per cm.2 It is deduced that the irregularities are at a height of about 400 km. They are most pronounced around midnight and exhibit little annual variation. The irregular portion of the ionosphere moves with a steady wind-like motion with a velocity of the order 100 to 300 m/s. The velocity decreases after midnight, and large velocities are associated with periods of magnetic disturbance.