The disturbed auroral ionosphere based on eiscat and rocket data

Abstract The common disturbed state of the ionosphere at auroral latitudes is dominated by ionisation due to fluxes of energetic charged particles. On the ground these “disturbances” can be identified by riometers which are sensitive to electron density enhancements in the D -region, and by the level of magnetic disturbance or figure K p which is indicative of currents in the E -region. Electron density profiles from 49,000 EISCAT UHF, 8000 EISCAT VHF and 108 rocket borne wave propagation data are processed jointly. Representative electron density profiles can be established as a function of season, solar zenith angle, solar activity, riometer absorption and K p . The validity of these profiles is tested in two ways: (a) by assessing deviations of measured electron densities from corresponding model values, and (b) by comparing the observed riometer absorption with the simulated absorption values derived from model electron densities representative of observed absorption levels. On average the modelled electron density model profiles agree with the rocket measurements to within a factor of 3.6 from the D - to the E -region.