Ionospheric D and E region plasma density enhancements caused by X17-class solar flare on September 7, 2005 - an Arecibo perspective.

On September 7, 2005 at 1740 UT, Earth orbiting satellies detected a major X17-class solar flare coming from the Sun's eastern limb. The blast caused a complete blackout of HF radio transmissions on the daylit side of Earth. The Arecibo Incohenrent scatter radar was operating as part of the World Month campaign. The radar's power profile (60-500 km) and coded long pulse (CLP) Ion Line experiments were used to get D, E, and F region electron density profiles, and E and F region spectra for temperature, composition, and velocity measurements. High resolution (150 m) plasma line profiles using the observatory's new digital receiver were measured during part of the period. Returned scattered power profiles indicated great enhancement in the D and E region, allowing us to estimate the density enhancement due to this large solar flare. Theoretical support is provided with the Data-Driven D region electron density model together with the Ionospheric Forecast Model developed by the Space Environment Corporation