HIGHLY NONLINEAR MAGNETIC PULSES AT COMET GIACOBINI-ZINNER

Nonlinear solitary magnetic pulses have been detected near the outbound bow shock/wave of Comet Giacobini‐Zinner. The pulses have peak field‐to‐background compression ratios ranging from 2.3 to 7.0 and full‐width half‐maximum durations from 12 to 72s, comparable to the H2O group ion gyroperiod. The waves air nearly circularly polarized and typically propagate at large angles (55°–75°) relative to the ambient magnetic field. The waves are all right‐hand polarized in the spacecraft frame, independent of their direction of propagation relative to the solar wind. Because all of the solitary waves have the same spacecraftframe polarizations, one interesting hypothesis is that the waves may have phase speeds greater than the solar wind speed The role that the waves may play with the bow shock is discussed briefly. Copyright 1990 by the American Geophysical Union.