Geophys. Res. Lett., 25, 23, 4297 - 4300, 1998
Abstract:
Examination of 770 days of heliospheric magnetic field data recorded within
polar solar wind by the Ulysses spacecraft revealed a number of occasions
when the wave power decreased by more than an order of magnitude for
several hours. These power dropouts were found to be associated with intervals
when the magnetic field was closely aligned with the radial direction. A
case by case study showed that there was no obvious signature in bulk
plasma parameters. A statistical study of 24 intervals when the field was close
to radial for at least 6 hours showed that the wave power in those intervals
was significantly lower than that outside. There were no significant
power changes when the field lay close to either the Parker spiral or
an arbitrary direction. Although they are likely to be of solar origin,
the exact source for these events is not clear.
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