Solar flare signatures of the ionospheric GPS total electron content

Abstract

In this study, ionospheric solar flare effects on the total electron content (TEC) and associated time rate of change (rTEC) derived from ground-based global positioning system (GPS) receivers in the midday region are examined. The occurrence times and locations of 11 solar flares are isolated from the 1-8 Å X-ray radiations of the geosynchronous operational environmental satellite (GOES) and the SOHO Extreme Ultraviolet Imaging Telescope (EIT) images, respectively, while the TEC and rTEC are obtained from the international GPS services (IGS). Results show that the maximum value of the TEC increase solely depends on the flare class, while the maximum value of the rTEC increase is related to not only the flare class but also the time rate of change in flare radiations. A statistical analysis further demonstrates that the two maximum values are inversely proportional to the cosine of the great circle angle between the center and flare locations on the solar disc. Copyright 2006 by the American Geophysical Union.