Variations in ionospheric parameters during solar flares

• Published in: Geomagnetism and Aeronomy 2009-12, Vol.49 (7), p.983-989
• Main Authors: Leonovich, L. A., Tashchilin, A. V.
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Global positioning systems; GPS; Ionosphere; Radar; Research methodology; Solar flares; Thermal expansion
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S001679320907024X

Results of studying the ionospheric response to solar flares, obtained based on the incoherent scatter radar observations of the GPS signals and as a result of the model simulations, are presented. The method, based on the effect of partial “shadowing” of the atmosphere by the globe, has been used to analyze the GPS data. This method made it possible to estimate the value of a change in the electron content in the upper ionosphere during the solar flare of July 14, 2000. It has been shown that a flare can cause a decrease in the electron content at heights of the upper ionosphere ( h > 300 km) according to the GPS data. Similar effects in the formation of a negative disturbance in the ionospheric F region were also observed during the solar flares of May 21 and 23, 1967, at the Arecibo incoherent scatter radar. The mechanism by which negative disturbances are formed in the upper ionosphere during solar flares has been studied based on the theoretical model of the ionosphere-plasmasphere coupling. It has been shown that an intense ejection of O + ions into the above located plasmasphere under the action of a sharp increase in the ion production rate and the thermal expansion of the ionospheric plasma cause the formation of a negative disturbance in the electron concentration in the upper ionosphere.