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

Results from the June 1998 combined ionospheric campaign (CIC) are presente d. The CI represents an attempt to focus a large number of different instru ments on one interesting geophysical region. The Center for Ionospheric Res earch (CIR) at Applied Research Laboratories, the University of Texas at Au stin (ARL:UT), has had several computerized ionospheric tomography (CIT) re ceivers 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 a t Arecibo to try to obtain an understanding of the temporal and spatial dis tribution of ionospheric structure observed during the campaign. We use the three data sets as inputs to the 3DVAR tomography algorithm developed at C IR and present results of the 3DVAR "objectively analyzed" electron density held. An ionization wall was found near 40 degrees latitude in agreement w ith previous Millstone Hill and DMSP observations in high Kp. Several elong ated density depletions were also detected.