An Analysis of Whistler-Mode Radiation from the Spacelab-2 Electron Beam. Revision.

During the shuttles Spacelab-2 mission, the Plasma Diagnostics Package PDP was released from the shuttle to freefly. At times during this freeflight when the PDP was magnetically connected to the shuttle, the Fast Pulsed Electron Generator FPEG, located in the shuttle cargo bay, ejected a 1 keV - 50 mA electron beam. The plasma wave instrument on board the PDP detected intense whistler mode radiation during these beam ejections. This paper presents a study of a whistler mode emission detected during one particular continuous electron beam firing. Calculations indicate that the beam radiated approximately 1.6 mW in the whistler mode as the beam transversed the 200 meters from the shuttle to the PDP. The emissivity also decreased by about a factor of 10 over this same distance. The measured wave powers are 10 to the 7th power greater than wave powers expected from incoherent Cerenkov radiation, verifying that the radiation is generated by a coherent process. Estimates of the emissivity based on measured electric field intensities in the beam indicate that the whistler mode noise is produced by radiation from electron bunches created by an electrostatic beam plasma instability.