coronal holes


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coronal holes

Regions of exceptionally low density and temperature compared with the surrounding solar or stellar corona. They overlie areas of the Sun's disk that are characterized by relatively weak divergent (and therefore primarily unipolar) magnetic fields, and are thought to be the primary source of the high-speed streams of energetic charged particles in the solar wind.
References in periodicals archive ?
When the Sun is quiet, the greater extent of the chromosphere above the poles is associated with the presence of large anchored coronal holes in this region [section](4.
Coronal holes become visible at random locations throughout the Sun, indicating the reorientation of hydrogen planes in the interior.
Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle.
Japan's Hinode sun-watching satellite photographed the sun's two coronal holes on Feb.
SXI also will monitor coronal holes -- persistent sources of high-speed solar wind.
Because the team has determined the geometry of the coronal holes, researchers can predict the speed of the solar wind.
This behavior suggested that coronal holes have the same cellular magnetic structure as the newly observed Coronal Cells, but that this structure is not visible until the encroachment of opposite-polarity flux causes some of the open magnetic flux in the holes to close.
The coronal cells occur in areas between coronal holes - colder and less dense areas of the corona seen as dark regions in images and "filament channels" which mark the boundaries between sections of upward-pointing magnetic fields and downward-pointing ones.
Right now, most of the solar wind is coming from coronal holes, or openings in the sun's magnetic field, but later in the year, the scientists expect coronal mass ejections (SN: 2/1/97, p.
During the decline of the sunspot cycle coronal holes develop and extend to the Sun's equatorial regions.