Combined ionospheric effect due to Forbush decreases and magnetospheric high energy particles at mid-latitudes

Abstract

After geoactive solar flares the Forbush decrease of galactic cosmic rays and magnetospheric high energy particles can cause opposite ionization effects in the ionospheric D-region at mid-latitudes. This has been shown by the change of the ELF and VLF atmospheric radio noise level and that of the LF absorption. The frequency dependence of these variations has been interpreted by waveguide mode theory and full-wave solutions using D-region electron density profiles under conditions characteristic of these ionization disturbances.