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 Previous: The Amateur Radio Crossword Puzzler |  Next: ARRL Urges Employers to Be Flexible in Leave Time for Volunteers |
The GOES-12 Satellite X-Ray Image showing the active region of the sun as of 2050 UTC on September 7. The dim green disk is the sun, while the bright spot is the flare. [NOAA/SEC Image] |
NEWINGTON, CT, Sep 7, 2005--One of the largest solar flares on record occurred today as a very active solar region 808 produced a powerful X17.1 flare--a "severe" or R4 event on NOAA's R1 to R5 scale. NOAA's GOES-12 satellite observed the flare at 1740 UTC. R4 events typically occur about eight times during each 11-year solar cycle, and today's was the fourth largest in 15 years.
"This event created a complete blackout of high-frequency (HF) communications on the daylit side of Earth," NOAA's Space Environment Center (SEC) reported. "Communications used by emergency services along the Gulf Coast may have experienced problems due to this flare. Low frequency navigation systems may also have experienced a period of significant degradation." R4 events also can disrupt satellites.
The effects of the X17.1-class solar flare began at 1717 UTC, peaked at 1740 UTC and ended at 1803 UTC. X-ray flux exceeded M5 at 1726 UTC.
A very bright and fast coronal mass ejection was observed, but the material was not Earth directed. An S1 to S2 is expected following this eruption, but it won't begin until late today or early September 8.
The GOES-12 X-ray flux chart. [NOAA/SEC Graphic] |
Over the past two weeks, the same active region of the sun has produced a series of significant solar eruptions as it made its passage around the back side of the sun. "Significant eruptions are expected in the coming days," the SEC said. "Agencies impacted by space weather storms may experience disruptions over the next two weeks. These include spacecraft operations, electric power systems, HF communications, and low-frequency navigation systems."
As of 2030 UTC, the SEC was reporting minor (R1) radio blackout conditions. That means weak or minor degradation of HF radio communication on Earth's sunlit side and occasional loss of radio contact.
Solar activity is expected to be moderate to high. Old region 798 is rotating onto the visible disk and is expected to significantly increase solar activity levels.
The September 7 event drove the Boulder 24-hour running A index up to 15 between 1500 and 1800 UTC. The Boulder K index for the same period was 3.
More information is available on the SEC Web site.
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