Submitted to J. Geophys. Res., 103, 29633-29642, 1998
The interplanetary shock observed by Ulysses on day 109 of 1992 occurred at a time of unusual interplanetary magnetic field conditions when the field was closely aligned with the radial direction for nearly a day ahead of the shock. There were several intervals of wave activity in the upstream region, the first occurring on day 108, and the second two intervals on day 109 leading up to the shock. In addition just ahead of the shock the background field magnitude decreased to a value close to zero and superimposed on this decrease were a number of field magnitude enhancements. The downstream region was populated by large amplitude compressive waves. A combination of spectral and wave analysis techniques were used to characterise the different intervals of wave activity. The waves on day 108 and the first interval of wave activity on day 109, are consistent with generation by an ion beam instability, but the waves on day 109 increased in amplitude as the shock was approached, suggesting that these waves were directly produced by the shock.
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