Combined ionospheric campaign 1: Ionospheric tomography and GPS total electron count (TEC) depletions

Results from the June 1998 combined ionospheric campaign (CIC) are presented. The CI represents an attempt to focus a large number of different instruments on one interesting geophysical region. The Center for Ionospheric Research (CIR) at Applied Research Laboratories, the University of Texas at Austin (ARL:UT), has had several computerized ionospheric tomography (CIT) receivers deployed in the Caribbean region since July 1997. In this paper we compare CIT data, GPS TEC data and data from the incoherent scatter radar at Arecibo to try to obtain an understanding of the temporal and spatial distribution of ionospheric structure observed during the campaign. We use the three data sets as inputs to the 3DVAR tomography algorithm developed at CIR and present results of the 3DVAR "objectively analyzed" electron density held. An ionization wall was found near 40 degrees latitude in agreement with previous Millstone Hill and DMSP observations in high Kp. Several elongated density depletions were also detected.