:Product: Weekly Highlights and Forecasts :Issued: 2003 Jul 22 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 14 - 20 July 2003 Solar activity was at low levels. Several moderate sized regions dominated the visible disk and produced numerous C-class flares. Region 409 (N15, L=193, class/area Fkc/490 on 15 July) was prominent early in the period, producing several C-class flares including a C8 at 14/0120 UTC. Activity on 15 – 16 July consisted of minor C-class flares from Regions 409 and 410 (S12, L=194, class/area Eac/620 on 20 July). On 16 July, Region 412 (N16, L=202 class/area Dai/200 on 17 July) appeared on the visible disk and exhibited steady growth for the next two days. By 17 July, it produced a C9/1n flare at 0823 UTC with associated Type II (988 km/s) and Type IV radio sweeps. A faint halo CME was seen but faded within the LASCO/C2 field of view. Decay noted in Region 409 on 18 July was offset by significant development in Region 410, and to a lesser extent Region 412. Region 410 exhibited considerable growth and developed a beta-gamma-delta magnetic configuration on 19 – 20 July. The period 18-20 July was highlighted by frequent C-class flares, primarily from Regions 410, 412, and a new region that emerged rather quickly on 20 July – Region 417 (S22, L=204 class/area Dso/110 on 20 July). Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. The period began with a short-lived return to near ambient solar wind speed (450 km/s). By late on the 14th, a co-rotating interaction region was detected at ACE, marking the onset of yet another high speed coronal hole stream. Solar wind speeds exhibited a gradual rise through early on the 15th and maintained an elevated 600 – 700 km/s through the 18th. Magnetic field measurements on the 16th would suggest that transient flow was embedded in the high speed stream. Solar wind speed returned to near 500 km/s for most of the 18th, but returned to a 600 - 700 km/s range by the 19th – 20th. There were no greater than 10 MeV proton events at geosynchronous orbit during the period. The greater than 2 MeV electron flux at geo-synchronous orbit reached high levels on 14 – 15, 17 –18, and 20 July. The period began with predominantly unsettled to active levels due to waning effects of a large coronal hole. A second coronal hole high speed stream rotated into a geoeffective position on 15 July. This resulted in minor storm levels on 15 July, major storm levels on 16 July, and an isolated minor storm period on 17 July. Embedded transient flow likely contributed to the most active periods on the 16th. Solar wind speed during this high speed stream reached maximum values near 700 km/s. The 18th saw a return to mostly quiet to unsettled levels with isolated active periods. The period ended with predominantly unsettled to minor storm levels in response to elevated solar wind speeds in the 600 – 700 km/s range. Forecast of Solar and Geomagnetic Activity 23 July - 18 August 2003 Solar activity is expected to be at low to moderate levels, with the possibility of some high intervals. Regions 410 and 412 have the potential for M-class events until they rotate beyond the west limb on 26 July. There is a slight chance of a major event from Region 410. Old Region 397 (N12, L=032) is due to return to the visible disk on 24 July and is expected to have M-class potential. This block of active longitudes currently on the visible disk (L = 190 – 205) will return by mid August and may produce moderate solar activity levels. There is a slight chance of a greater than 10 MeV proton event at geosynchronous orbit early in the period. The greater than 2 MeV electron flux is expected to reach high levels on 30 July – 04 August, 09 - 11 August, and again on 12 –17 August, due to recurrent coronal hole high speed streams. The geomagnetic field is expected to range from quiet to major storm levels during the period. A large, recurrent coronal hole high speed stream in expected to become geoeffective on 28 July – 03 August, and produce active to minor storm levels. Coronal hole effects are expected again on 7 - 9 August and again on 11 – 17 August and occasional minor storm periods are possible. Isolated major storm periods are possible with these high speed steams, but will be mostly confined to high latitudes in local nighttime hours.