Pick of The Week
 
 

Coronal Holes and Aurora (October 8, 2003)

Hi-res TIF image (1.7M)

Movies:
MPEG: Large (1.7M), Small (572K)
Quicktime: Large (701K), Small (177K)

Hi-res TIF image (5.3M)

This week the Sun had a good-sized coronal hole that rotated into a position on the right side of the Sun where it could have generated aurora on Earth. Coronal holes, which appear as darker areas in SOHO's ultraviolet imagers, are a source of the higher speed solar wind. The magnetic field in coronal holes opens outward, allowing electrically charged particles to escape and be accelerated by the solar wind. Elsewhere in the Sun's outer atmosphere, the magnetic field curves back toward the surface and traps nearly all charged particles close to the Sun. The density and speed of the solar wind coming from coronal holes are significantly higher than in the solar wind originating over "closed" magnetic field regions.

When these "high speed streams" from coronal holes sweep past the earth, the charged particles interact with the atoms and molecules of the gases in the Earth's upper atmosphere, leading to the auroral glow. October is usually a good time to look for auroras, so our friends in Canada and other higher latitude regions like the northern tier states of the U.S., keep your eyes to the skies!

The movie from EIT (in fourteen times ionized iron) shows solar activity and the coronal hole as it rotates around almost to the Sun's edge. The auroral image was taken near Québec this summer by Michel Tournay. Thanks for sharing it with us, Michel!

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Previous Picks of the Week

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.

If your institution would also like to receive the same Weekly Pick from us for display (usually in Photoshop or QuickTime format), please send your inquiry to steele.hill@gsfc.nasa.gov.

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