:Product: Weekly Highlights and Forecasts :Issued: 2003 Dec 10 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 01 - 07 December 2003 Solar activity was at low to moderate levels this period. The period began at low levels with Region 508 (S17, L=284, class/area Ekc/480 on 23 November) as the likely source of the modest C-class activity. Region 508, though in decay, maintained considerable complexity as it rotated around the west limb on 01 December. Activity increased to moderate levels on 02 December with a number of X-ray events occurring on the southwest limb. The most likely source of this activity was Region 508. The first of these limb events was a C7 flare that occurred at 02/0948 UTC, followed by a significant long duration X-ray enhancement that peaked at 1145 UTC. LASCO and EIT imagery observed a full halo CME from this event, with a measured mean plane-of-sky speed at 1234 km/sec. Two M1 flares were also observed from this region, at 1308 and 2300 UTC. Activity returned to low levels from 03 – 05 December, with occasional weak C-class flares observed. The frequency of the C-class activity increased late on 05 December with majority of the activity originating in Region 510 (S23, L=228, class/area Dai/150 on 28 November). Activity increased to moderate levels on the 6th with Region 510 producing an M1 and M2 flare at 1120 UTC and 1546 UTC. Activity returned to low levels on 07 December. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. The period began with slightly elevated solar wind speeds due to a coronal hole. Solar wind plasma and IMF measurements were at nominal levels from 02 - 04 December. Early on the 5th, solar wind speed, temperature, and density increased. Total IMF also increased to near 20 nT and Bz ranged –5 to –18 nT for several hours. The signature was consistent with a co-rotating interaction region (CIR) preceding a high speed coronal hole stream; however, it is likely that the enhancement also included transient material from the 02 December CME. The weak high speed stream persisted through the 6th, before declining to near 400 km/s by early on then 7th. The gradual onset of another high speed stream was observed late on the 7th. On 02 December, the greater than 10 MeV protons reached event threshold at 1505 UTC and shortly after, hit a maximum flux of 88.9 pfu at 1820 UTC. Flux levels decayed below event levels at 0000 UTC on 04 December. Protons remained elevated through 05 December. The most likely source of this event was the long duration X-ray enhancement and CME on 02 December. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels on 04, 06, and 07 December. The geomagnetic field ranged from quiet to severe storm levels. The period began with slightly elevated solar wind speeds, which produced isolated active conditions at all latitudes. Quiet to unsettled periods prevailed from 02 – 04 December. A combined high speed stream and transient impact on 05 December produced unsettled to major storm periods with occasional severe storm levels observed at high latitudes. Predominantly quiet to minor storm periods were observed on the 6th and 7th, with occasional major storm periods at high latitudes. Forecast of Solar and Geomagnetic Activity 10 December 2003 - 05 January 2004 Solar activity is expected to range from very low to moderate levels. Activity is expected to be at low levels early in the period. Active longitudes are due to return to the visible disk by mid December and may produce moderate levels. Expect mostly low activity levels by early January. There is a small chance for a greater than 10 MeV proton event from mid to late December. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on 10 – 15 December, 19 – 23 December, and again on 03 – 05 January. The geomagnetic field is expected to range from quiet to major storm levels. A large trans-equatorial coronal hole has moved into a geoeffective position and is expected to produce active to major storming through 14 December. Unsettled to minor storm periods are expected on 18 - 22 December, and again on 01 - 05 January due to high speed coronal hole streams.