:Product: Weekly Highlights and Forecasts :Issued: 2002 May 28 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 May 2002 Solar activity ranged from low to high levels. Activity was high on 20 May due to two impulsive major flares from Region 9961 (S22, L = 331, class/area Eai/480 on 20 May): an M5 at 20/1053 UTC and an X2/2n at 20/1527 UTC. Region 9961 produced C-class subflares during the rest of the period. It began to gradually decay on 24 May, though a magnetic delta persisted within its intermediate spots until 25 May. Activity was moderate on 21 and 24 May with isolated, lesser M-class flares from Regions 9960 and 9963. Region 9960 (N14, L = 347, class/area Dac/140 on 21 May) also produced C-class subflares during the period. It contained a delta within its trailer spots until 25 May, then began to decay and simplify. Region 9963 (N15, L = 316, class/area Dho/420 on 23 May) was stable in terms of size and complexity through most of the period, but showed minor spot growth on the last day of the period. The highlight of the period was a large filament eruption from the southwest quadrant on 22 May. The eruption was associated with a long-duration C5 parallel-ribbon flare at 22/0354 UTC, a fast full-halo CME (plane of sky velocity approx. 1500 km/sec), and a >10 MeV proton event. Region 9957 (N10, L = 010, class/area Ekc/830 on 19 May) produced isolated C-class subflares during the period. It gradually decayed during the period, but was of interest due to delta magnetic configurations within its northern and southern spot clusters. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. A relatively weak CME passage occurred on 21 – 22 May associated with enhanced velocities (peaks to around 500 km/sec). Two CME passages occurred on 23 May. The first shock passed ACE at around 23/1000 UTC as solar wind speeds increased from 400 to 600 km/sec. IMF Bz turned strongly southward following the shock with maximum southerly deflections to minus 43 nT (GSM) at around 23/1130 UTC. The second shock passed the spacecraft at approximately 23/1500 UTC, which boosted winds speeds to near 1000 km/sec for a short period. CME effects subsided late on 23 May. A weak high-speed stream associated with a recurrent coronal hole was observed on 25 May associated with a brief enhancement of solar wind velocities (peaks in the 500 to 550 km/sec range). A greater than 10 MeV proton event followed the filament eruption of 22 May. It began at 22/1755 UTC, reached a maximum of 820 pfu at 23/1055 UTC, and ended at 24/1455 UTC. Greater than 10 MeV flux levels returned to background levels on 25 May. Greater than 2 MeV electron fluxes at geo-synchronous orbit were at normal to moderate levels. Geomagnetic field activity was at mostly quiet to unsettled levels through 22 May. Activity increased to active to severe storm levels on 23 May following a sudden storm commencement at 1051 UTC (87 nT, Boulder USGS magnetometer). Severe storm levels occurred during 23/1200 – 1800 UTC. This storm was associated with the filament eruption and halo CME on 22 May. The storm ended late on 23 May. Activity was at mostly quiet levels for the rest of the period. Forecast of Solar and Geomagnetic Activity 29 May - 24 June 2002 Solar activity is expected to be at low to moderate levels during the period. Isolated low-level M-class flares are likely. There is a slight chance for isolated major flare activity during the period. There will be a slight chance for a proton event during the period. Greater than 2 MeV electron fluxes at geo-synchronous orbit are expected to be at normal to moderate levels for most of the period. Quiet to unsettled geomagnetic field levels are expected for most of the period. However, active conditions are possible around 23 June. .