:Product: Weekly Highlights and Forecasts :Issued: 2003 Sep 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 August 2003 Solar activity was at low levels. Region 436 (N07, L=89, class/area Eac/230 on 22 August) was the most active region during the period and produced the largest flare, a C4/1n at 1559 UTC on 26 August. Region 436 was in gradual decay at the beginning of the period and rotated beyond the west limb on 29 August. On 28 August, a C1 flare occurred at 1335 UTC with an associated Type II radio sweep (800 km/s). There were two potential sources of the C1/Type II: one from a flare located in Region 445 (N03, L=016, class/area Dao/110 on 27 August) and the second from a flare on the southeast limb (S10). On 30 – 31 August, Region 442(S12, L=025 class/area Dso/160 on 23 August) produced two long duration C1 flares. The first one occurred at 0514 UTC on 30 August and the second occurred at 0622 UTC on 31 August. The second C1 was associated with a CME off the southwest limb, but did not have an Earth directed component. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. The period began on 25 August with solar wind speed near 600 km/s due to a coronal hole high speed stream. By 26 August solar wind speed was in steady decline and reached 425 km/s on 28 August. Late on 29 August a transient pass the ACE spacecraft with solar wind speed increasing to 650 km/s and Bz dropping to near –10 nT for a two hour period. The transient effects began to diminish late on 30 August and solar wind speed was back down to 400 km/s by 31 August. 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 everyday of the period (25 – 31 August). Geomagnetic activity ranged from quiet to minor storm levels. Activity on 25 August was at unsettled to minor storm levels as the high speed stream began to diminished. Activity on 26 – 29 August was at quiet to active levels. On 30 August, activity was mostly at quiet to active levels with one period on isolated minor storm levels. The period ended on 31 August at quiet to unsettled levels. Forecast of Solar and Geomagnetic Activity 03 - 29 September 2003 Solar activity is expected to range from very low to low levels during the period. There is a slight chance of isolated moderate activity from old Region 431 (S13, L= 194) when it returns on 04 September. 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 05 – 07 September, 10 – 12 September and again on 20 – 22 September. The geomagnetic field is expected to range from quiet to major storm levels. A coronal hole high speed stream is expected to produce active to minor storm conditions on 03 – 05 September. Minor storm levels are possible from a smaller high speed stream on 08 – 09 September. Later in the period a third coronal hole high speed stream is expected to return with active to major storm levels possible on 17 – 21 September.