Ionospheric observations of the November 1993 storm

Complementary measurements from three different electron density measurement techniques are presented for the time period of the November 4, 1993, storm. Computerized ionospheric tomography (CIT) data from an array of nine ground stations operating as part of the Mid-America CIT Experiment (MACE 93) is presented along with data from a digital ionosonde operating near the midpoint of the CIT array. Corroborating data from the DMSP satellites are also presented. Taken together the data provide evidence of a strongly disturbed ionosphere with rapid variations of electron density structures in space and time. The CIT data show a deep equatorward surge of the the midlatitude trough to nearly 50 degrees geomagnetic latitude, while the ionosonde shows dramatic variations in the virtual height of the ionosphere. DMSP data confirm the equatorward surge of the trough and also display a number of sharp latitudinal variations in vertical drift velocities. An interesting occurrence of spread F also occurred during this time period.