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Order Returning To Solar Wind After Period Of Chaos
Order is returning to the solar wind as the Sun begins to shake off
the chaos that has characterized its behavior during the recent peak
in its 11-year activity cycle.

"Since the last part of August, Ulysses appears to be back at the edge
of the prolonged high speed solar polar wind," says George Gloeckler,
from the University of Maryland, who is principal investigator of the
Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses.

The re-emergence of the high speed wind from the Sun's north polar
regions, which the spacecraft is presently crossing, is a sign that
the activity is subsiding and the Sun is beginning to settle down once
more to a quiet time.

During maximum solar activity, the polarity of the Sun's magnetic
field changes: the north pole takes on the polarity of the south pole
and vice versa.

"The magnetic polarity that accompanies this high speed solar wind
stream is the new polarity," says Andre Balogh, from Imperial College,
London, who is principal investigator for the magnetometer experiment
on Ulysses.

The Sun is settling down at high latitudes where Ulysses is journeying
now. But solar storms are still raging near the equator -- some have
hit the Earth very recently.

"There may be turmoil yet near the equatorial region, but Ulysses has
started observing conditions which will eventually prevail all around
the Sun," says Balogh.

Recent images taken by SOHO, ESA's Solar and Heliospheric Observatory,
also reveal that the Sun's shift to the new cycle is asymmetrical. In
the SOHO image on the left, the dark area around the north pole, from
which the high speed solar wind is emerging, is not yet matched by a
similar region around the south pole. This should change over the
coming months as the Sun's activity diminishes.

The last time Ulysses observed quiet conditions over the entire Sun
was during the spacecraft's first six-year solar polar orbit when the
Sun was at or near solar minimum. Then, Ulysses discovered that the
boundary between high speed wind streaming away from the poles, and
low speed wind emanating from lower latitudes, is quite distinct.

Last year, when the Sun's activity peaked, Ulysses flew above the
Sun's south pole for the second time and found a solar wind of slow or
intermediate speed, just as it had seen at lower latitudes during the
build up to maximum.

The spacecraft will continue to make observations for at least the
next two years as the Sun's activity subsides towards the next
minimum. Once Ulysses has completed its current north polar passage,
it will embark once again on the long leg of its circuit out towards
Jupiter's orbit.
[Contact: Dr. Richard Marsden]

09-Oct-2001