:Product: Weekly Highlights and Forecasts :Issued: 2004 Nov 02 2212 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Environment Center # Product description and SEC contact on the Web # http://www.sec.noaa.gov/weekly.html # # Weekly Highlights and Forecasts # Highlights of Solar and Geomagnetic Activity 25 - 31 October 2004 Solar activity ranged from low to high this period. Low levels occurred on 25 - 29 October, but activity quickly rose to high by the 30th. The summary period ended on 31 October with moderate activity levels. Region 691 (N13, L=139, class/area, Dac/270 on 31 October) accounted for a majority of the significant activity with most of that occurring on 30 October. This region grew quickly toward the end of the 29th as new opposite polarity spots emerged around the leader spot and fueled instability that resulted in major flares. Chronologically for the 30th, Region 691 produced: a C9/Sf with type II sweep at 0049 UTC, an M3/Sf with type II sweep at 0333 UTC, an M4/Sf Tenflare with a type II sweep at 0618 UTC, an M3/1N with type II sweep at 0928 UTC, an X1/Sf (partially obscured by clouds) Tenflare with type II and IV sweeps at 1146 UTC, and an M5/Sn Tenflare with type II sweep at 1633 UTC. Numerous large radio bursts occurred throughout the period of major flaring. A scarcity of LASCO observations made it difficult to discern if associated CMEs occurred, but a nearly full halo CME after the M5 event was visible in C2 at 1654 UTC with a plane-of-sky velocity of between 700 – 800 km/s. The CME was not symmetric and most of the material appeared to be moving away from the southwest limb. New Region 693 (S16, L=075, class/area, Fkc/760 on 31 October) rotated onto the disk on the 27th as a bright plage region, but grew rapidly in white light both in spot count and area. The region has shown some magnetic complexity but has produced only low-level C-class activity. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. Solar wind speed ranged from a low of near 300 km/s early on 29 October to a high near 525 km/s midday on 25 October. The period began under the influence of a weak, geoeffective coronal hole wind stream as solar wind speed approached 525 km/s and the IMF Bz oscillated between +/- 8 nT throughout much of the 25th. By early on 26 October, wind plasma measurements stabilized and remained stable through 28 October. Early on the 29th, the IMF Bz began to fluctuate between +10 and -8 nT; temperature, density, and solar wind speed increased, indicative of a co-rotating interactive region followed by a weak coronal hole wind stream. Wind speed slowly climbed to 500 km/s by midday on 31 October and ended the period near 450 km/s while the IMF Bz ended the period stable, not varying much beyond +/- 5 nT. There were no greater than 10 MeV proton events at geo-synchronous orbit during the summary period. However, a greater than 10 MeV proton enhancement was observed following the high solar activity on 30 October. At the time of this writing, a relatively small, but energetic proton event had occurred following a bright CME, originating from behind the west limb early on 01 November. The greater than 2 MeV electron flux at geosynchronous orbit was at normal levels on 25 - 30 October and moderate levels on 31 October. The geomagnetic field was at mostly quiet to unsettled levels with brief periods of active conditions at mid latitudes midday on the 25 October and again during the first half of 30 October. Isolated periods of minor to major storming were observed at high latitudes midday on 25 and 29 – 31 October, all due to effects from geoeffective coronal hole wind streams. Forecast of Solar and Geomagnetic Activity 03 - 29 November 2004 Solar activity is expected to be low to moderate throughout most of the forecast period due to possible M-class flare activity from Regions 691 and 693. A greater than 10 MeV proton event is possible with major flare activity from Regions 691 and 693. The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at high levels on 03 – 04 November and again on 10 – 13 November. The geomagnetic field is expected to be mostly quiet to unsettled for the majority of the forecast period. On 09 – 11 November, a recurrent coronal hole wind stream is expected to produce occasional active to minor storm periods with isolated major storm periods at high latitudes.