:Product: Weekly Highlights and Forecasts :Issued: 2003 Mar 25 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 17 - 23 March 2003 Solar activity ranged from low to high levels. The most significant region during the period was Region 314 (S14, L=60, class/area/mag. Eki/500/Bgd on 18 March). The region was in a rapid growth phase on 17 – 18 March and was the source of most of the activity during the period. On 17 and 18 March, Region 314 produced two X1.5/1b flares, one at 17/1905 UTC and the second at 18/1208 UTC. The X1.5 flare on 18 March was associated with a Type II (507 km/s) and Type IV radio burst, a ten-centimeter radio burst (1400 sfu), and a full halo CME. Region 314 also produced two M-class events and numerous C-class events on 18 March. Activity declined to moderate levels on 19 March with four M-class flares from Region 314, the largest an M3.7/1n at 19/0953 UTC. Moderate levels persisted through 20 March as Region 314 produced an M1/1f flare. Region 314 entered a slight decay phase on 19 March and rotated beyond the west limb on 21 March. For the remainder of the period, 21 – 23 March, activity was at low levels with numerous B-class and minor C-class flare from Region 314. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft for most of the summary period. On 17 March, solar wind velocity was near 700 km/s due to a continuing coronal hole high speed stream. This high speed stream increased to near 800 km/s late on 17 March and into 18 March, then began to gradually decline. A CME shock from the X1.5 flare on 18 March arrived at the ACE spacecraft late on 19 March and peak solar wind velocities reached 850 km/s early on the next day. The shock arrival resulted in a rotation of structured Bz, first oriented northward, then a 3-4 hour period of southward Bz by midday on 20 March. Solar wind velocity on 21 – 23 March was in a gradual decline from around 700 km/s down to 600 km/s at the close of the period. The declining but still elevated solar wind is due to residual coronal hole high speed stream effects. There were no greater than 10 MeV proton events at geo-synchronous orbit during the summary period. The greater than 2 MeV electron flux at geo-synchronous orbit reached high levels on each day of the period, 17 – 23 March. The geomagnetic field ranged from quiet to major storm levels. The period began with unsettled to major storm levels on 17 March due to continuing effects from a large equatorial coronal hole and associated high speed stream. Activity gradually declined on 18 – 19 March with minor storm levels and active levels respectively. A CME shock that arrived late on 20 March produced active to minor storm conditions late on 20 March and into 21 March. Activity for the remainder of the period, 22 – 23 March, was predominantly at unsettled to active levels. One period of isolated major storm conditions was observed on 23 March due to elevated solar wind and periods of southward fluctuations in the Bz component of the interplanetary magnetic field. Forecast of Solar and Geomagnetic Activity 26 March - 21 April 2003 Solar activity is expected to be at low to moderate levels. Activity is expected to be at low levels until the return of Region 306 and Region 314 on 02 and 03 April respectively. Low level activity with a chance of moderate activity is expected on 04 – 17 April. No greater than 10 MeV proton events are expected during the forecast period. The greater than 2 MeV electron flux may reach high levels on 27 – 28 March, 04 – 06 April and again on 14 – 19 April due to returning coronal holes. The geomagnetic field is expected to be at quiet to major storm levels during the period. Two small but intense coronal hole streams are due on 25 – 27 March and 30 – 31 March and are expected to produce active to isolated major storm levels. A weak but persistent coronal hole stream is expected on 01 – 04 April with unsettled to isolated active conditions. The large equatorial coronal hole is due to return to a geo-effective position on 10 – 14 April. .