Aurora Borealis Observed on September 10, 2005

1. Event Overview

An aurora borealis occurred during the overnight hours of September 10, 2005, visible in the United States as far south as Arizona. The tri-state region was no exception as generally clear skies and an early moonset allowed for great viewing. Recent major solar flares associated with an active sunspot region (Region 808) on the Sun were responsible for producing a severe geomagnetic storm. According to a space weather advisory issued on the morning of September 11, 2005 by the NOAA's Space Environment Center (SEC), since sunspot Region 808 made its appearance on the surface of the Sun on September 07, it had produced five strong (R3) radio blackouts, and one severe (R4) radio blackout (the fourth largest flare in the past fifteen years). The sunspot region had shown little signs of weakening. Additional significant solar flares were expected for the next ten to eleven days as that large region moved across the Sun. The geomagnetic storm was responsible for disrupting electric power systems to various agencies including, Spacecraft operations, HF communications, and navigation systems such as GPS.

Fig. 1. Sunspot Region 808 on the Sun. Image courtsey SOHO /MDI.

2. Pictures

The following pictures were taken four miles east of Goodland, Kansas between 12:00 and 12:30 am MDT (0600 - 0630 UTC). The colors began with a bright band of green and ended with greens, reds and oranges. Note the red "columns". The columns were observed moving rapidly east to west across the northern sky. Mouse click on the images to view full size.

 

3. Data

Values of an index to measure geomagnetic activity, known as the Kp index, rapidly increased over the region starting on the evening of September 10, 2005. By midnight MDT indices began to peak at nine. For the magnetic latitude of Goodland, an optimal Kp value to view the aurora is nine. The figure on the right shows the trend in the Kp index. For more information on what the Kp index is, and how to determine optimal viewing conditions for your location, visit the SEC website.
http://www.sec.noaa.gov/Aurora/index.html

Fig. 2. A plot spanning the overnight hours of 10 September 2005, containing the estimated planetary K-index. K-indices of 5 or greater indicate storm-level geomagnetic activity. Image courtsey SEC.

 

The figure to the right shows the extent and position of the auroral oval from the North Pole; valid near the time the photos above were taken. The image is extrapolated from measurements obtained from the most recent polar pass of the NOAA POES satellite.

Fig. 3. Extent and position of the auroral oval valid 0631 UTC, 11 September 2005. Image courtsey SEC.

Solar X-ray imagery of the Sun obtained from a geostationary satellite captured the flares emitted from sunspot Region 808. The flares in the imagery appear as bright regions.

Fig. 4. GOES-12 solar X-ray image, valid 0600 UTC, 11 September 2005. Note the bright area is associated with Region 808. Image courtsey SEC.
--AEP

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