:Product: Weekly Highlights and Forecasts :Issued: 2003 Dec 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 December 2003 Solar activity was at very low to moderate levels during the period. The largest, and most active region was Region 528 (N10, L=261, class/area Fkc/740 on 25 December). This region exhibited steady areal growth early in the period and a slow steady decay after 26 December. Activity from Region 528 consisted of nineteen C-class flares including two long duration events, a C5/Sf at 0825 UTC on 25 December and a C7/1f at 1038 UTC on 26 December. A weak partial halo CME was associated with the long duration C5 on the 25th. This region also produced the largest event of the period, an M1/1n at 1928 UTC on 26 December. The other region of interest during the period was Region 525 (N10, L=291, class/area Dsi/130 on 21 December). This region produced six C-class flares before it dissipated on the disk on 26 December. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. The period began with elevated solar wind speeds near 625 km/s due to residual effects from a small coronal hole high speed stream. On 23 December, solar wind speed began a steady decline that reached 375 km/s by 25 December. A weak transient passed the ACE spacecraft at 0900 UTC on 27 December and was likely the effects of a weak CME from the long duration C5 on 25 December. Wind speeds finished the period near 525 km/s. 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 reached high levels on 22 – 25 December. The geomagnetic field ranged from quiet to active levels. Isolated active periods were observed on 22 December and again on 27 December. Forecast of Solar and Geomagnetic Activity 31 December 2003 - 26 January 2004 Solar activity is expected to be at very low to low levels. A slight chance of moderate level activity is possible from Region 528 for the first two days of the period. Expect mostly very low to low activity levels for the remainder of the period. No greater than 10 MeV proton events at geosynchronous orbit are expected during the period. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on 02 – 03 January and again on 06 – 14 January due to recurrent coronal holes. Geomagnetic activity is expected to range from quiet major storm levels. Unsettled to minor storm periods are expected on 01 – 02 January due to a small coronal hole high speed stream. A large transequatorial coronal hole is expected to return 04 –10 January and major storm periods are expected.