Highlights of Solar and Geomagnetic Activity
21 - 27 May 2007

Solar activity was very low. Isolated B-class flares occurred during most days including a B3 at 22/1447 UTC and a B5 at 23/0732 UTC, both of which were associated with Type II radio sweeps.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux events at geosynchronous orbit reached high levels during 24 - 27 May.

Geomagnetic field activity was at quiet to unsettled levels on 21 May. Activity increased to quiet to active levels on 22 May with a brief minor storm period detected at high latitudes. A further increase to quiet to major storm levels occurred on 23 May with a brief severe storm period detected at high latitudes.

The 22 - 23 May disturbance was due to a coronal mass ejection passage associated with a 19 May filament disappearance from old Region 956 (N03, L =071, class/area Dkc/300 on 17 May).

ACE solar wind data indicated the CME passage began late on 21 May with increased IMF total field intensity (which reached a peak of 14.3 nT at 22/0514 UTC) and periods of sustained southward IMF Bz (minimum - 11.3 nT at
23/0932 UTC). A recurrent coronal hole high-speed stream influenced the field during 24 - 27 May.

Field activity ranged from quiet to major storm levels during this time. ACE data indicated a peak velocity of 750 km/sec at 26/1123 UTC and minimum IMF Bz of -6.9 nT at 24/1350 UTC associated with the high-speed stream. Proton densities reached a peak of 35.5 p/cc at 22/2340 UTC in advance of the high-speed stream.

Forecast of Solar and Geomagnetic Activity
30 May - 25 June 2007

Solar activity is expected to be at very low to low levels. Isolated C-class flares are possible during 08 - 21 June due to the return of old Region 956 to the visible disk.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels during 30 May - 03 June, 17 June and 20 - 25 June.

Quiet conditions are expected during 30 May - 02 June. Activity is expected to increase to quiet to active levels during 03 - 04 June due to a recurrent coronal hole high-speed stream. Activity is expected to decrease to mostly quiet levels during 05 - 13 June.

An increase to unsettled to active periods is expected during 14 - 15 June due to a recurrent coronal hole high-speed stream. Quiet to unsettled conditions are expected during 16 - 19 June.

Another recurrent coronal hole high-speed stream is expected to affect the field during 20 - 23 June. Unsettled to minor storm conditions are expected during this time with major storm periods possible at high latitudes. Activity is expected to decrease to quiet to unsettled levels during 24 - 25 June.

Prepared by the US Dept. of Commerce, NOAA, Space Environment Center