SPACE WEATHER ADVISORY BULLETIN #03- 2 2003 October 21 at 06:11 p.m. MDT (2003 October 22 0011 UTC) **** INTENSE ACTIVE REGIONS EMERGE ON SUN **** Two very dynamic centers of activity have emerged on the sun. NOAA Region 484 developed rapidly over the past three days and is now one of the largest sunspot clusters to emerge during Solar Cycle 23, approximately 10 times larger than Earth. This region, which is nearing the center of the solar disk, already produced a major flare (category R3 Radio Blackout on the NOAA Space Weather Scales) on 19 October at 1650 UTC. The region continues to grow, and additional substantial flare activity is likely. A second intense active region is rotating around the southeast limb of the sun. Though the sunspot group is not yet visible, two powerful eruptions occurred on 21 October as seen from the LASCO instrument on the SOHO spacecraft. These eruptions may herald the arrival of a volatile active center with the potential to impact various Earth systems. Further major eruptions are possible from these active regions as they rotate across the face of the sun over the next two weeks. Agencies impacted by solar flare radio blackouts, geomagnetic storms, and solar radiation storms may experience disruptions over this two-week period. These include satellite and other spacecraft operations, power systems, HF communications, and navigation systems. Full Halo CME on 2003/10/23, frontshided LASCO and EIT observed a 'full halo CME' on 2003/10/23. The event was first observed in C2 at 08:54 UT as a bright loop front over the E limb; this had developed to a full halo CME by 00:30 UT, albeit faint in the W. The front first appeared in C3 at 09:18 UT with full coverage of the C3 occultor by 10:20 UT. Note that the emission in the W is brighter in C3 than C2, though still faint by comparison to that in the E. The mean plane-of-sky speed for this event was 1110 km/s at PA69, with possible evidence for moderate deceleration. The CME was probably associated with an X5.4 X-ray flare observed by EIT between 08:24 - 09:24 UT, centered at S10E55 with peak emission at 08:36 UT. Note that very strong emission is also seen to the E of this, around S10E75. GOES records this flare from AR 0486 between 08:19 - 08:49 UT with peak emission at 08:35 UT. A very large EIT wave, and dimming were observed in association with this event. Considering the location of the flare, the faint emission in the W hemisphere and ongoing activity in the region between AR 0486 and AR 0484 centered N04E13 during this period, this event has been determined frontsided. Oct 24, 2003 Shift Report -------------------------- Radiation Shutdown. SCS 107 run by command at ~ 297:13:34 GMT. At the 09:15 (EDT) radiation telecon we noted ACE rates above 120,000. This would exceed ACIS fluence budget, even for the interval from next ACIS observation to the next following COMM opportunity. Furthermore, a shock wave and at least one more CME is on the way, so we can anticipated an extended period of high rates, perhaps even for 2 more days. For the HRC observation 3732 in progress, background is about 3 times normal, and we are guessing this will not compromise the primary objective of separating the emission from the two components.