ALFVEN MODULATION OF THE SUBSTORM MAGNETOTAIL TRANSPORT

This work explores the proposition that magnetic field resonances modu late the transport of particle and magnetic flux in the earth's magnet otail. Coordinated high- and low-altitude measurements during a substo rm show periodic variations of magnetic field, plasma density and flow bursts in the magnetotail with frequencies that correlate well with t hose of magnetic field oscillations at geosynchronous altitude and pul sations measured by ground-based stations. The pulsations' frequency i s in the Pc 5 range. The example presented here occurred during the su bstorm period of May 19-20, 1996, that was chosen as the first ISTP/GG S campaign for the groundbased and theory investigations. There appear s to be a resonance between modes sustained by the near-Earth magnetic field and compressional and flapping pulsations that can be sustained by the magnetotail.