:Product: Weekly Highlights and Forecasts :Issued: 2004 Aug 17 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 09 - 15 August 2004 Solar activity levels ranged from low to high. The summary period began with low levels on 09 – 11 August, increased to moderate on 12 August, and further increased to high on 13 - 15 August. Region 656 (S13, L=082, class/area, Fkc/1360 on 13 August) produced most of the activity this period with 63 C-class flares, 17 M-class flares, and 1 X-class flare. The period began with a slow, faint CME visible in LASCO C2 imagery off the south limb beginning at about 10/1854 UTC. The CME was associated with surge activity and a subsequent EIT wave that was observed just north of Region 656 and east of central meridian. The largest flare of the period was an X1.0/1n, with an associated 180 sfu 10cm burst, observed on 13/1812 UTC. Significant activity was also observed on 14 and 15 August when Region 656 produced multiple M-class flares. On 14 August, an M7.4/2n (0544 UTC) and an M5.6/2N (1343 UTC) were reported. During this period, SOHO/LASCO imagery depicted several CMEs that all appeared to have a solar westward component. On 15 August, multiple M-class flare activity was once again observed, the largest an M9.4/1n that occurred at 1241 UTC. A faint, CME was seen on SOHO/LASCO imagery, but did not appear to be Earth-directed. Old Region 652 quietly rotated around the east limb on the 12th and was numbered Region 661 (N07, L=348, class/area, Dko/390 on 15 August). Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. The period began on 09 August with solar wind speed near 400 km/s. Early on 10 August, wind speed showed an increasing trend and peaked near 650 km/s by early on 11 August. The increase in velocity and temperature, and a subsequent decrease in density, was consistent with the onset of a high-speed coronal hole wind stream. The IMF Bz responded with variations of +/- 7 nT through midday on the 10th and did not vary beyond +/- 5 nT through late on 13 August. Wind speed slowly decayed for the next few days and ended the summary period near 400 km/s. At approximately 13/2200 UTC, a weak shock passed the ACE spacecraft and was most likely associated with the faint halo CME observed late on 10 August. Wind speed jumped briefly to near 500 km/s for about 2 hours. The IMF Bz rotated +/- 7 nT for about 6 hours and then remained mostly northward 3 – 5 nT for the remainder of the summary period. There were no greater than 10 MeV proton events at geosynchronous orbit during the summary period. The greater than 2 MeV electron flux at geosynchronous orbit was at high levels on 11 – 14 August. The geomagnetic field ranged from quiet to active levels. The period began with quiet to active levels on 09 – 11 August as a recurrent coronal hole high speed stream influenced the geomagnetic field. Thereafter, activity declined to quiet to unsettled levels, and remained so through the end of the summary period. Forecast of Solar and Geomagnetic Activity 18 August - 13 September 2004 Solar activity is expected to range from very low to high. Solar activity is expected to be at moderate to high levels through 17 and 18 August. Activity should begin to diminish on 19 August as Region 656 transits the western solar limb. Activity levels are expected to decrease to very low to low through late August. Thereafter, and through to the end of the forecast period, activity levels are expected to increase to low to moderate when old Region 656 (L=082) is due to return. A greater than 10 MeV proton event is possible through 19 August and again after 01 September upon the return of old Region 656. The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at high levels on 24 – 26 August and 04 – 06 September. The geomagnetic field is expected to range from quiet to unsettled levels for most of the forecast period. From 23 – 25 August and again on 03 – 05 September, levels are expected to increase to unsettled to active due to a pair of weak, recurrent coronal hole streams that are expected to be in a geoeffective position.