Official Space Weather Advisory issued by NOAA Space Environment Center Boulder, Colorado, USA

SPACE WEATHER ADVISORY BULLETIN #05- 2

2005 January 17 at 12:37 p.m. MST (2005 January 17 1937 UTC)

**** LARGE ACTIVE REGION PRODUCES STRONG SOLAR STORMS ****

The large and dynamic active sunspot region, numbered by NOAA as Region 720, has produced several strong solar events. Five large solar flares produced moderate (R2) to strong (R3) radio blackouts since 15 January. The largest of these solar eruptions, an X3.8 on the GOES-12 x-ray sensor, occurred today at 17/0659 UTC (near local midnight MST). Short-wave radio communications through the sunlit hemisphere of Earth experienced significant signal degradation during these solar flares.

Associated strong geomagnetic and radiation storms are underway. The radiation storm began on 16/0210 UTC (15 January, 7:10 P.M. MST) and is currently at the S3 (strong level). A G3 (strong) geomagnetic storm began early on the 17th (UTC) and remains in progress. The geomagnetic storm is associated with two coronal mass ejections (CMEs) observed on SOHO/LASCO imagery on 15 January.

A third Earth-directed CME was observed today following the X3.8 flare. This CME is expected to impact the geomagnetic field on 17 and 18 January with strong (G3) to severe (G4) geomagnetic storm levels. The radiation storm in progress now is expected to continue for several more days.

Active Region 720 is a large and complex sunspot cluster. Further major eruptions are possible from this region before it rotates around the visible solar disk on 22 January. Agencies impacted by solar flare radio blackouts, geomagnetic storms, and solar radiation storms should continue to closely monitor the space environment through the remainder of this week.

Data used to provide space weather services are contributed by NOAA, USAF, NASA, NSF, USGS, the International Space Environment Services and other observatories, universities, and institutions. For more information, including email services, see SEC's Space Weather Advisories Web site http://sec.noaa.gov/advisories or (303) 497-5127.

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