:Product: Weekly Highlights and Forecasts :Issued: 2002 Mar 26 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 18 - 24 March 2002 Solar activity was at low to moderate levels. Region 9866 (S09, L = 191, class/area Eki/900 on 12 March) produced long-duration low-level M-class flares during March 18 – 19 and 22, as well as a long-duration C-class flare on March 20 (for flare specifics, please refer to the Energetic Events or Optical Flares lists). Imagery from the NASA SOHO/LASCO sensor indicated each of these flares was associated with a halo or partial-halo CME. Region 9866 rotated out of view on March 22 following a period of gradual decay. Region 9878 (N09, L = 038, Fao/150 on 23 March) produced isolated C-class subflares late in the period. It had moderate magnetic complexity and was in a gradual growth phase as the period ended. Solar wind data were available from NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. Three CME passages occurred during the period following flare activity in Region 9866. The first shock arrived at ACE at around 18/1237 UTC accompanied by an abrupt increase in velocity (peaks to around 500 km/sec), total IMF field intensity, density, and temperature. IMF Bz was mostly northward during this passage. The second CME arrived at ACE at 20/1307 UTC. Velocities increased from around 430 km/sec to 600 km/sec following the shock. IMF Bz turned briefly southward (peak deflections to minus 10 nT (GSM) following the shock, then turned northward after 20/1600 UTC. The final CME reached ACE at 23/1054 UTC associated with increased velocities (peaks to around 500 km/sec); and relatively minor increases in temperature, density, and IMF total field intensity. IMF Bz was variable at plus 10 nT to minus 05 nT (GSM) following the shock arrival, but turned mostly southward during approximately 23/2000 – 24/1500 UTC with peak southward deflections to minus 12 nT (GSM). Greater than 10 MeV proton events occurred at geo-synchronous orbit on March 18, 20, and 22 - 23. CME shock-accelerated particles pushed the greater than 10 MeV flux above event threshold during March 18 – 20 and 22 (the greater than 10 MeV flux was already enhanced in the wake of a proton event on March 17 - see PRF #1385). Peak flux during this period was 53 pfu at 19/0650 UTC. Another greater than 10 MeV proton event began at 22/2020 UTC following a long-duration M1 limb-flare from Region 9866. This event reached a peak of 16 pfu at 23/1320 UTC, then ended at 23/2030 UTC. Greater than 2 MeV electron fluxes were at normal levels through the period. Geomagnetic field activity increased to unsettled to active periods during March 18 – 20 and 23 with brief minor storm conditions on March 19. Sudden impulses (SI) occurred at 18/1323 UTC (42 nT), and 20/1329 UTC (11 nT). A sudden storm commencement (SSC) was observed at 23/1137 UTC (16 nT) as well, followed by active to (brief) major storm conditions on March 24. This activity followed multiple CME passages associated with the long-duration flare activity in Region 9866 mentioned above. Forecast of Solar and Geomagnetic Activity 27 March - 22 April 2002 Solar activity is expected to be at low to moderate levels. Isolated, low-level M-class flares are likely during the period. Greater than 2 MeV electron fluxes will be at normal to moderate levels during most of the period. However, high flux levels are possible during April 04 – 05. There will be a slight chance for a proton event during the latter half of the period. Geomagnetic field activity is expected to be at quiet to unsettled levels during most of the period. However, active periods are likely during April 02 – 03 due to a high speed solar wind stream associated with a recurrent coronal hole. .