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Aurora Borealis---November 7-8 , 2004
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Aurora
Borealis...November 7-8, 2004
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On
the night of November 7th and into the early morning of the 8th, the inland
northwest was showered with a spectacular display of Northern Lights or
Aurora Borealis.
The Aurora is defined as glowing,
visual phenomenon associated with geomagnetic activity, which occurs mainly
in the high-latitude night sky. The glow comes from pulses of solar geomagnetic
energy bombarding or exciting magnetically charged particles in the ionosphere,
roughly 100 to 250km above the ground.
Although eastern Washington
and north Idaho do not commonly witness these fascinating light shows,
they typically happen a handful of times during the year. The rarity of
the events in the inland northwest can be attributed to our mid-latitude
location and the amount of cloudiness we typically see.
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Click on images for larger picture.
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The
electromagnetic energy which produces the aurora phenomena is measured
by the NOAA Space Center, utilizing an index termed the Kp Index. Although
this is a difficult index to calculate, the resultant values correlate
to the chances of witnessing an aurora at a given location.
The map at the left shows what
the minimum value of the Kp index needs to be to at your location in order
to possibly witness the aurora. A value of 5 or 6 (or greater ) suggests
that most of the inland northwest could possibly witness auroral activity.
Of course factors such as moonlight, city light pollution, and cloud cover
will impact the visibility of the auroral activity.
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The
night of the auroral activity featured a Kp index value of 10 with reports
of the northern lights being seen as far south as Oklahoma. The graph
on the right corresponds to the Kp index levels over a 72 hour period.
The times are in Universal Time Coordinates, which run 7 hours ahead of
Pacific Standard Time.
This
graph is produced every hour at the following link:
http://www.sec.noaa.gov/rt_plots/kp_3d.html
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Webmaster
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
Spokane Weather Forecast Office
2601 N. Rambo Rd.
Spokane, Washington 99224
Tel: (509) 244-0110
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