:Product: Weekly Highlights and Forecasts :Issued: 2004 Aug 03 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 26 July - 01 August 2004 Solar activity levels ranged from very low to moderate. The summary period began with moderate activity on 26 and 27 July as Region 652 (N08, L=345, class/area, Fkc/1060 on 26 July) produced minor M-class flares. Early on 28 July, a long duration (~5.5 hours) C4 enhancement that peaked at 0609 UTC was observed from Region 652. LASCO imagery showed a large CME off the west limb with some of the westward-directed ejecta Earth bound. By 29 July, activity levels returned to moderate as an M2 x-ray event was observed at 29/0006 UTC. The most significant event of the day was a long duration C2 flare from Region 652 with an associated Earth-directed partial halo CME. Activity levels decreased to low on 30 July as Region 652 rotated around the west limb. By 31 July, old Region 652 had rotated further beyond the west limb, yet produced a C8 long duration (~4 hours) x-ray enhancement that peaked at 0657 UTC. The summary period ended on 01 August with activity levels at very low. 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 speed near 600 km/s as transient effects from a series of CMEs from 22 and 23 July were still present. At 26/2228 UTC, a strong sudden impulse (SI) of 95 nT was observed at the Boulder magnetometer. This SI followed the very fast (~31 hours) transit of the full halo CME associated with the long duration M1 flare of 25 July. Solar wind speed increased from the already elevated levels near 600 km/s to over 1050 km/s. After nearly four hours of fluctuating between -15 and +15 nT, the IMF Bz rotated strong southward and ranged from -15 to -25 nT for about 15 hours. Thereafter, and for the remainder of the summary period, the Bz ranged from between +5 to –5 nT. Wind speed gradually decreased to near 500 km/s through most of 30 July. At 30/2115 UTC, a weak SI (25 nT) occurred at Boulder with a brief increase in wind velocity to 600 km/s. This SI was believed to be in response to the long duration C4 x-ray event on the 28th. Wind speed gradually decreased to 500 km/s and ended the summary period near 450 km/s. Another weak shock passage was observed at the ACE spacecraft at approximately 01/0130 UTC and was believed to be the result of the long duration C2 x-ray flare observed on 29 July. The greater than 10 MeV proton event that began on 25/1855 UTC reached a peak flux of 2,090 pfu on 26/2250 UTC and ended on 28/0040 UTC. The event was associated with the long duration M1 flare on 25 July and had an initial peak of 271 pfu on 26/1905 UTC. The larger peak on 26/2250 UTC was associated with the shock passage following the very fast transit of the full halo CME from the M1 flare. The greater than 2 MeV electron flux at geosynchronous orbit was at high levels on 26 – 27 July and 01 August and at very high levels on 28 – 31 July. The geomagnetic field ranged from quiet to severe storm levels. The period began on 26 July with activity at major storm levels as transient effects from a series of CMEs from 22 and 23 July were felt. By 27 July, activity increased to severe storm levels as the geomagnetic field responded to effects from the long duration M1 flare of 25 July. By 28 July, the field had relaxed to quiet to unsettled conditions and remained so for the remainder of the summary period. Forecast of Solar and Geomagnetic Activity 04 - 30 August 2004 Solar activity is expected to range from very low to low. Activity levels are expected to increase to low to moderate after 12 August when old Region 652 (L=348) is due to return. A greater than 10 MeV proton event is possible after the return of old Region 652. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on 08 – 10 August. Early in the forecast period, from 07 to 09 August, the geomagnetic field is expected to range from mostly unsettled to active levels due to a weak, recurrent coronal hole stream that is expected to be in a geoeffective position. Thereafter through the end of the forecast period, mostly quiet to unsettled conditions are expected.