:Product: Weekly Highlights and Forecasts :Issued: 2004 Mar 23 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 15 - 21 March 2004 Solar activity ranged from low to moderate with the bulk of this period’s activity originating from two new regions, regions 574 and 578. Region 574 (S04, L=177, class/area, Esi/120 on 20 March) rotated onto the disk on 16 March and produced this period’s largest event, an M1.6/2b flare on 18/0517 UTC. The most active region on the disk was Region 578 (N15, L=144, class/area, Eao/180 on 21 March) that rotated onto the disk on 18 March. Since first appearing, Region 578 has produced 20 mostly low-level C-class flares and one M-class flare; an M1.5/1f on 18/2236 UTC. Both regions exhibited slow, steady growth as they transited the disk. During the period, 4 CME’s were clearly visible in LASCO imagery, but none were Earth directed. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. The period began with solar wind velocities at speeds averaging 450 km/s with a brief spike to 550 km/s midday on 16 March. By 17 March, wind speeds began to gradually decrease and weakened to just over 325 km/s by early on 19 March. Thereafter, wind velocities began another gradual increase, ending the summary period at about 425 km/s. The elevated solar wind speeds early in the period were driven by remnants of a favorably positioned, recurrent coronal hole and by 17 March, effects of the coronal hole were gone. The Bz component of the interplanetary magnetic field did not vary much beyond +/- 5 nT for the entire 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 for the entire summary period. The geomagnetic field ranged from mostly quiet to unsettled levels with isolated active periods observed early on 15 March and again midday, at high latitudes, on 21 March. The early active period was due to waning effects of the previous week’s large coronal hole. Forecast of Solar and Geomagnetic Activity 24 March - 19 April 2004 Solar activity is expected to range from low to moderate levels throughout the forecast period. Isolated moderate activity is possible from Region 574 until its departure on 29 March and from Region 578 until its departure on 31 March. From 31 March through 11 April, activity should be at mostly very low to low levels. Solar activity is expected to increase to low to moderate levels after old regions 574 (11 April) and 578 (13 April) return. No greater than 10 MeV proton events are expected during the period. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on from 27 to 29 March, 06 to 11 April and again on 19 April due to recurrent coronal holes. Geomagnetic activity is expected to range from quiet to minor storm levels. A weak coronal hole high-speed stream is due to return on 26 – 27 March and is expected to produce unsettled to active conditions. A large, recurrent coronal hole high-speed stream is due to return on 05 – 09 April and is expected to produce active to minor storm conditions. Unsettled to active conditions are expected on 17 to 18 April due to weak coronal hole high-speed stream.