RADIO INTERFEROMETER MEASUREMENTS OF PLASMASPHERE DENSITY STRUCTURES DURING GEOMAGNETIC STORMS

The Los Alamos plasmaspheric drift radio interferometer is a ground-ba sed array that regularly measures periodic disturbances in the plasmas phere. These plasmaspheric density structures have been shown to depen d on geomagnetic activity, as indicated by Kp. However, a direct storm time analysis of their behavior has not been done. This paper studies the amplitude, drift velocity, and location of these structures befor e, during, and after the onset of major geomagnetic storms. Distinct l arge-amplitude, storm time signatures are found during the first night after onset, continuing through the third night; there were significa ntly more storm time signatures during nighttime than daytime. The L s hells on which the disturbances existed were found to decrease after s torm onset, indicating a possible shrinking of the plasmasphere.