:Product: Weekly Highlights and Forecasts :Issued: 2003 Oct 29 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 20 - 26 October 2003 Solar activity ranged from moderate to high levels. Moderate levels were observed on the 20th and 21st due to low M-class activity in Region 484 (N04, L=354, class/area Ekc/1750 on 23 October). On 22 October, Region 486 (S15, L=282, class/area Fkc/2200 on 25 October) rotated onto the visible disk producing several M-class flares including an M9 at 2007 UTC. An Earth directed CME was also observed on the 22nd originating in Region 484. High levels were observed on the 23rd with Region 486 producing two major flares – an X5/1b at 0835 UTC and an X1/1n flare at 2004 UTC. The X5 was the largest event of the period and had an associated Type II radio sweep (967 km/s) and a CME that was not Earth directed. Activity on 24 October was at high levels due to an M7/1n flare at 0254 UTC. Moderate level activity on 25 October included two long duration M1 flares - an M1/2n at 0446 UTC from Region 486 and an M1/Sf at 0553 UTC from Region 484. The latter event was associated with a Type II radio sweep. Activity on the 26th returned to high levels with two long duration X1 flares. The first event was an X1/3b from Regon 486 that occurred at 0654 UTC and was associated with Type II (1302 km/s) and Type IV radio sweeps. The second event was an X1/1n from Region 484 that occurred at 1819 UTC with an associated Type II (950 km/s) and a partial halo CME off to the west. At the Time of this report issue: Region 486 produced one of the largest flares of this solar cycle, an X17/4B proton flare peaking at 1110 UTC on 28 October. A very fast (near 2000 km/s), earthward directed halo CME was associated with this flare as well as a Type II (1250 km/s) and Type IV radio sweep. Region 486, with over 2100 millionths of white light areal coverage, is now one of the largest and most complex active regions of solar cycle 23. The X17 flare produced proton events at greater than 10 and greater than 100 MeV which remain in progress at this time. The greater than 100 MeV event began at 1145 UTC with a maximum so far of 176 pfu. The greater than 10 MeV proton event began at 1215 UTC with a maximum so far of 6020 pfu. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. Early in the period solar wind speed was elevated near 750 km/s due to a coronal hole high speed stream. By 22 October wind speed was in decline and decreased to 400 km/s by early on 24 October. An interplanetary shock from the X5 flare on the 23rd was observed at ACE at 1450 UTC on 24 October with a 200 km/s jump in solar wind speed and total IMF measurement near 30 nT. Bz during and after this interplanetary shock remained mostly northward. There was one greater than 10 MeV proton event at geosynchronous orbit during the period. The proton event began at 1825 UTC on 26 October, reached a peak value of 466 pfu at 2335 UTC and ended at 1910 UTC on 27 October. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels on 20 – 24 October. Geomagnetic activity ranged from quiet to severe storm levels. Activity on 20 – 22 October reached minor storm levels with one period of isolated major storm levels on 22 October. This activity was due to coronal hole high speed stream effects. On 24 October, with the arrival of the interplanetary shock mentioned above activity reached severe storm levels for a brief period following a sudden impulse on the Boulder magnetometer at 1530 UTC. By 25 October activity was at quiet to active levels. The period ended on 26 October with quiet to unsettled levels. Forecast of Solar and Geomagnetic Activity 29 October - 24 November 2003 Solar activity is expected to range from low to high levels. Regions 486 and 488 have the potential for M and X-class activity during the first week of the period. After these regions rotate beyond the west limb on 04 – 05 November, activity is expected to be low to moderate. Currently a greater than 10 MeV proton event is in progress and is expected to continue through the first three days of the period. Additional proton producing flares are likely while Regions 486 and 488 remain on the visible disk. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on 12 – 19 November due to a large returning coronal hole. The geomagnetic field is expected to range from quiet to severe storm levels during the period. The CME from the X17 flare is due to arrive late on day one or early on day two of the period. Severe geomagnetic activity is expected from the CME. A large coronal hole is due to return on 09 – 18 November and is expected to produce major storm levels.