Ionospheric electron concentration imaging using GPS over the USA during the storm of July 2000

A new technique for ionospheric imaging is demonstrated during a severe geomagnetic storm of 15th July 2000. The three‐dimensional time‐dependent imaging algorithm is applied to multi‐directional ground‐based GPS data and yields spatial maps of electron concentration. This technique is demonstrated by showing a series of images of the mid‐latitude ionosphere over the USA during the storm of July 2000. A strong uplift in the height of the F‐layer is observed after 20 UT on 15th July, followed by a severe latitudinal electron concentration gradient. Independent verification of the images is provided by the ionosondes and incoherent scatter radar data. The GPS images reveal the large‐scale dynamics of the ionosphere during the disturbed conditions and show the potential of geophysical imaging for storm‐time ionospheric studies.