Wave propagation effects of broadband electrostatic noise in the magnetotail

An analysis of the wave and particle data from ISEE 1 for 1978 yielded several examples of crossings between the lobe and the plasma sheet boundary layer (PSBL) which exhibited the signatures predicted by the theoretical analysis of the generation of broadband electrostatic noise (BEN) by ion beam instabilities. These signatures are a gradual rise in the upper frequency of BEN as the spacecraft approaches the plasma boundary layer, and a very rapid rise in the upper frequency near the crossing into the PSBL from the lobe. Several examples of crossings are presented that exhibit both signatures, as well as a case of crossings in which the gradual frequency rise signature is absent but the rapid rise is present. This case exhibits a BEN in the range expected for the low-frequency ion-ion two-stream and the high-frequency Buneman instability.