Substantial Coronal Hole (February 6, 2004)
Hi-res TIF image (3.6M)
The Earth is being bathed in a solar stream that is flowing out of
this large coronal hole observed over an eight-day period (Jan. 27 -
Feb. 3, 2004). Coronal holes appear as dark areas of the corona when
viewed in ultraviolet light and in X-rays. This coronal hole area is
one of the larger ones seen over the past year. Coronal holes are the
source of strong solar wind gusts that carry solar particles out to
our magnetosphere and beyond. Solar wind streams take 2-3 days to
travel from the Sun to Earth, and the coronal holes in which they
originate are more likely to affect Earth after they have rotated
more than halfway around the visible hemisphere of the Sun. As you
can see, this hole has maintained its shape fairly coherently as it
has rotated around from the left to right. And it may reappear when
the Sun rotates this area around again in about two weeks.
The magnetic field lines in a coronal hole open out into the solar
wind rather than connecting to a nearby part of the Sun's surface.
Coronal holes are responsible for the high-speed solar wind streams
that sweep through the plane where the planets orbit -- and thus have
a direct affect on "space weather" near the Earth. In fact, it is
anticipated that Earth will continue to experience mild geo-effective
storming for the next few days, particularly at the higher latitudes.
Thus, people living in those areas are likely to see some aurora
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