Ionospheric Effects of the X-Ray Flares of September 24, 2011 According to Oblique Sounding Data

UDC 550.388.2 We present the results of observations of a sudden wideband attenuation of short radio waves and Doppler-shift variations of the signals from broadcast stations on oblique sounding paths in the Eurasian longitudinal sector during a series of X-ray flares that occurred on September 24, 2011. The results of modeling of the electron-density profiles in the lower ionosphere based on measurements of attenuation of short waves on the Moscow — Rostov-on-Don path at a frequency of 9996 kHz of the standard-time RWM station during the most powerful flare that occurred on September 24, 2011 at 09:40 UT are given.