:Product: Weekly Highlights and Forecasts :Issued: 2003 Aug 19 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 11 - 17 August 2003 Solar activity was at very low to low levels. The period began on 11 August with very low level activity. For the remainder fo the period (12 – 17 August), activity was at low levels with numerous C-class flares from Region 431 (S13, L=194, class/area Ekc/500 on 14 August). Region 431 was the most active region during the period and produced numerous C-class flares on 12 – 14 August. This Region exhibited rapid growth to over 500 millionths on 13 – 14 August and developed a beta-gamma-delta magnetic configuration. The largest flare of the period was a long duration C7 from Region 431 on 15 August at 0018 UTC. Region 431 entered a gradual decay phase on 15 – 17 August and simplified to a beta-gamma magnetic configuration on 17 August. Although in decay, Region 431 was the source of numerous C-class flares on 15 – 17 August. Region 424 (S18, L=290, class/area Ekc/760 on 06 August) was in steady decay before it rotated beyond the west limb on 14 August. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. A coronal hole high speed flow began on day one of the period with solar wind speeds increasing from 550 km/s to a peak near 700 km/s on 12 August. Solar wind speed decreased back to 550 km/s over the next few days. Bz during 11 – 15 August was, on average, northward. A smaller high speed flow occurred on 15 August with peak solar wind speeds near 650 km/s, then promptly declined to 420 km/s by early on 17 August. A shock was observed at the ACE spacecraft at 1340 UTC on 17 August, marked by a 100 km/s jump in solar wind speed and an increase of 20 nT in the IMF total field. Bz was initially northward with minimal impact at Earth. At the time of this report writing (18 August), Bz has turned southward. At 0100 UTC on 18 August Bz turned sharply south and maintained this southward orientation for an extended period. There were no greater than 10 MeV proton events at geosynchronous orbit during the period. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels on 11 – 17 August. The geomagnetic field ranged from quiet to minor storm levels. The period began with quiet to active levels on 11 August. The coronal hole high speed flow early in the period produced brief periods of minor storm levels on 12 – 13 August and active conditions on 14 August. The smaller high speed flow on 15 August resulted in unsettled to active conditions on 15 August. Activity decreased to quiet to unsettled levels on 16 August. The shock that passed ACE on 17 August produced active conditions late on 17 August. At the time of this report writing (18 August), geomagnetic activity has reached severe storm levels. IMF Bz turned sharply southward on 18 August, initiating the significant disturbance. Activity was at minor to severe storm levels until 1500 UTC on 18 August. Forecast of Solar and Geomagnetic Activity 20 August - 15 September 2003 Solar activity is expected to range from very low to moderate levels during the period. Activity for most of the period is expected to be at very low to low levels. Region 431 may produce an isolated M-class event before it rotates off the disk on 21 August. No greater than 10 MeV proton events at geosynchronous orbit are expected during the period. The greater than 2 MeV electron flux is expected to reach high levels on 25 August – 01 September, 05 – 07 September, and again on 10 – 13 September. The geomagnetic field is expected to range from quiet to major storm levels during the period. A large coronal hole high speed flow is due to return to a geoeffective position on 22 August with minor to major storm levels possible on 22 – 29 August. Another coronal hole high speed flow is due on 02 – 05 September with minor to major storm levels possible. Towards the end of the period a couple smaller coronal holes may produce isolated minor storm levels.