:Product: Weekly Highlights and Forecasts :Issued: 2002 Apr 30 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 22 - 28 April 2002 Solar activity was at low to moderate levels during the summary period. Activity was moderate on 24 April due to an M1/1f flare at 24/2156 UTC from Region 9912 (N10, L= 069, class/area Dai/270 on 21 April). Activity was low during 22- 23 April and 25 - 28 April with predominantly minor C-class activity. Region 9912 produced a C2/Sf flare on 22/1210 UTC with an associated Type II radio sweep (estimated velocity 804 km/s). Other notable activity during the period included two filament eruptions. The first off the southwest quadrant on 22/2230 UTC with a non-Earth-directed CME. The second filament eruption occurred late in the day on 26 April at S32, L=003. This filament eruption also produced a large non-Earth-directed CME. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. A coronal mass ejection arrived at ACE on 23/0400 UTC with IMF Bz turning southward for approximately a half hour. Maximum deflection was minus 20 nT (GSM). Solar wind speed reached a maximum of about 670 km/s at 23/0500 UTC. After the CME shock passage solar wind speed gradually decayed until 28 April when it increased to approximately 550 km/s due to recurrent high speed stream effects. At the start of the summary period a greater than 100 MeV proton event and a greater than 10 MeV proton event were in progress due to the X1 west limb flare on 21 April. The greater than 100 MeV event began on 21 April 0155 UTC and ended on 22 April 2335 UTC (peak flux of 22.9 pfu on 21 April 1025 UTC). The greater than 10 MeV proton event began on 21 April 0225 UTC and ended on 26 April 0715 UTC (peak flux of 2520 pfu on 21 April 2320 UTC). The greater than 2 MeV electrons at geo-synchronous orbit were at high levels on 22 April due to the effects of the X1 flare on 21 April. Greater than 2 MeV electrons reached moderate levels on 26 - 27 April. Geomagnetic activity was at quiet to major storm levels during the summary period. Early on 23 April the CME shock arrived from the X1 flare on 21 April. A 60 nT sudden impulse was measured on the Boulder magnetometer and minor storm conditions resulted. An isolated severe storm period (09 - 12 UTC) was observed at the higher latitudes. On 24 - 27 April the geomagnetic field was quiet to unsettled. Late in the period, 28 April, activity increased to unsettled to active conditions with isolated major storming at high latitudes due the return of a high speed stream. Forecast of Solar and Geomagnetic Activity 01 - 27 May 2002 Solar activity is expected to be low to moderate with a chance of an isolated period of high activity early in the period. M-Class activity is expected during the first 1-2 weeks of the period due to returning active regions. During the later part of the period only C-class and isolated low-level M-class activity is expected. There is a sight chance of a proton event early in the forecast period in conjunction with the potential for increased solar activity. Greater than 2 MeV electron fluxes are expected for 01 - 02 May due to coronal hole effects. Normal to moderate flux levels are expected during the rest of the period. The geomagnetic field is expected to be quiet to unsettled during most of the period. Active conditions are possible on 24 - 27 May due to a returning coronal hole. .