Substantial Coronal Hole (March 12, 2003)
This week the most significant feature on the Sun is a large coronal
hole, whose leading edge has rotating past the central meridian as of
13 March 2003. The video clip shows the hole as it rotates with the
Sun from when it first appeared on 8 March. Coronal holes appear as
dark areas of the corona when viewed in ultraviolet light and in
X-rays. This distinctive hole area appears to extend across about one
fifth of this side of the Sun, the largest seen in about year or more
(see earlier Pick of the Week).|
Coronal holes are often 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 they are more likely to affect Earth after they have rotated more than halfway around the visible hemisphere of the Sun. Scientists are expecting a distinct increase in geomagnetic effects from the solar wind that originated from this hole. Aurora predictions at different latitudes can be found at spaceweather.com and actual conditions can be checked on our own site at http://soho.nascom.nasa.gov/spaceweather/
The magnetic field lines in a coronal hole extend out into the solar wind rather than connecting to a nearby part of the Sun's surface. Often located near the poles of the Sun, coronal holes also occur closer to the solar equator, as we see here. These low-latitude 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.
SOHO began its Weekly Pick some time after sending a weekly image or video clip to the American Museum of Natural History (Rose Center) in New York City. There, the SOHO Weekly Pick is displayed with some annotations on a large plasma display.
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