THE OBJECTIVE IS TO IDENTIFY IN 1-SECOND GROUND-MAGNETOMETER DATA LARGE DB/DT INTERVALS PLACE THEM INTO SOLAR WIND AND GEOMAGNETIC CONTEXT (STORM AND SUBSTORM CORRELATION) AND CHARACTERIZE THE SPECTRAL PROPERTIES OF THE EVENTS AT PREVIOUSLY UNDER-STUDIED HIGHFREQUENCY (ON THE ORDER OF HZ) SIGNATURES. WE WILL ANALYZE DECADES OF MAGNETOMETER DATA FROM SCORES OF STATIONS. OUR RECENT STUDIES HAVE FOUND: (1) THAT A SIGNIFICANT FRACTION (40%) OF THE LARGEST DB/DT EVENTS ARE NOT ASSOCIATED WITH SUBSTORMS AND (2) MANY OF THE LARGEST DB/DT WITHIN THE E3/GIC TIME DOMAIN ARE PRECEDED AND/OR ACCOMPANIED BY LARGE AND MORE RAPID FLUCTUATIONS (E2). FROM THIS LIST WE WILL IDENTIFY EVENTS THAT HAVE BOTH LEO (E.G. SWARM FAST) AND MAGNETOSPHERIC SATELLITE (E.G. VAN ALLEN PROBES MMS THEMIS) OBSERVATIONS. THOUGH MAPPING UNCERTAINTIES AND THE NEED TO HAVE BROAD CONJUNCTION CRITERIA WILL MAKE IT DIFFICULT TO FIND THE SAME EVENT ON THE GROUND AND IN SPACE WE WILL CHARACTERIZE THE FIELD SIGNATURES (E.G. DIPOLARIZATIONS COMPRESSIONS) AND WAVE PROPERTIES OF THE SPACE-BASED OBSERVATIONS TO PLACE THE EVENTS INTO GLOBAL CONTEXT. WE WILL THEN MODEL SELECT INTERVALS WITH BOTH MODELS TO UNDERSTAND THE CURRENT AND IONOSPHERIC ELECTRIC FIELD STRUCTURES RESPONSIBLE FOR THE FAST AND GIC SIGNATURES. WE WILL ADDRESS ALL THREE PRIMARY OBJECTIVES ((1) DETERMINE THE SPACE CONTEXT OF DB/DT (2) CHARACTERIZE THEIR TEMPORAL AND SPATIAL SCALES AND (3) USING OBSERVATIONS AND MODELS ESTIMATE THE IDEAL SPACING OF GROUND-BASED OBSERVATIONS) OF THE MAGNETOSPHERIC AND IONOSPHERIC PROCESSES RESPONSIBLE FOR RAPID GEOMAGNETIC CHANGES FST.