Satellite measurements of solar X-ray flux and their use for interpretation of sudden ionospheric disturbances

Summary The apparatus for the reception and evaluation of the real-time telemetry (RTT) data on the X-ray flux, measured by the satellite Solrad-9, is briefly described. A comparison of the RTT data obtained with the data published by the authors of the experiment shows a good correlation of the data compared. The results of the comparison of our RTT data with SID data of the Panská Ves Observatory confirm many known facts concerning the response of the lower ionosphere to solar flares and, moreover, seem to support the idea of a less important role of X-rays in the lower ionosphere under slightly disturbed conditions.