Total electron content changes in the ionosphere during the January 10, 1997 disturbance

We have used the CORS network of GPS receivers to record ionospheric TEC changes in the continental United States caused by the well observed geomagnetic disturbance of January 10, 1997. This event produced numerous worldwide consequences. Although the initial arrival of this disturbance was before sunrise in the U.S. the TEC levels were most significantly altered later during the daylight hours. We display temporal and spatial changes through time series at selected sites and maps of the entire network. The usual sequence of diurnal changes was not greatly altered, but most of the TEC values were increased by about a factor of one and a half to two. Stations in the northeast and upper north central were exceptions and showed a small decrease in TEC. We interpret the TEC changes as consequences of changes in neutral chemical composition resulting from storm heating.