Variations in ionospheric parameters during solar flares

Abstract

Results of studying the ionospheric response to solar flares, obtained based on the incoherent scat� ter 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 ion� osphere during the solar flare of July 14, 2000. It has been shown that a flare can cause a decrease in the elec� tron 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 distur� bances 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 concentra� tion in the upper ionosphere.