The production of free electrons in the ionosphericDlayer by solar and galactic cosmic rays and the resultant absorption of radio waves

The behavior of the D layer under bombardment by solar and galactic cosmic rays of energy greater than a few Mev is discussed. In particular, the variation with incident particle flux of the ionospheric parameters that determine the equilibrium electron density is deduced by means of the measurements of mid-day and mid-night absorption of cosmic radio noise corresponding to identical fluxes and spectrums of solar cosmic rays (protons). The values of the ionospheric parameters so obtained are then used in conjunction with differential solar proton spectrums of the form dJ/dP = Ke−p/p· to determine the electron densities and resultant absorption effects of cosmic radio noise in the range 3-30 Mc/s. Special attention is given to weak absorption effects in the ranges 3-10 Mc/s and to problems relating to the measurement of small, low-energy solar-particle events and to the changes in the low-energy portion of the spectrum of galactic cosmic rays.