Highlights of Solar and Geomagnetic Activity
Covering the period: 06 - 12 May 2024

Solar activity was high. The bulk of the activity came from Region 3664 (S17, L=347, Fkc/BGD on 10 May). This region was resonsible for 41 M-class and 9 X-class flares accounting for approximately 72% of the 74 energetic events observed during the week. It was also responsible for several CMEs, On Monday, 6 May the region had grown to an Ekc/BGD group, having been a numbered region since 01 May. By the 8th, it had more than doubled in size to 1200 microhemispheres.and had produced its first three X-class flares. By 10 May, it had doubled again in size to 2400 microhemispheres and produced a total of 6 X-class flares.

Flares and CMEs noted included the following from Region 3664, with flare maximum time and particulars followed by the time the CME was first visible in C2 imagery:

08/0509 X1.0 - 08/0600

To be determined, 08/1224

08/1753 M7.9/2N, 08/1912

08/2236 X1.0, 2140

09/0913, X2.2/3B; 09/0948.

These CMEs were all modeled in a 09/1300 Enlil run which prompted the dissemination of a G4 geomagnetic storm watch (See alerts listing). Additional flares and CMEs prior to the onset of the geomagnetic storm occurred at:

09/1744 X1.1/2B, 09/1912

10/0654 X3.9, 09/0748

11/0123 X5.8/2B, 11/0136

Note: The flare/CME associations are provisional at this point and may need revision. Please see the Energetic Events list for information regarding radio emissions associated with the flare described above, and for information regarding the remainder of the flares not described above. Additonal CMEs occurred in conjunction with the remaining flares but are not described here.

Proton events were observed at geosynchronous orbit. A 10 Mev at 10 pfu event, associated with an X3.9 flare from region 3664, began on 10 May at 1335, peaked at 207 pfu on 10/1745, and ended at 12/1235. A 100 MeV proton event, associated with an X5.8 flare from Region 3664, began on 11 May at 0210, reached a peak of 7 pfu at 11/0715, and ended at 12/0030.

The greater than 2 MeV electron flux at geosynchronous orbit was at normal to moderate levels.

Geomagnetic field activity reached extreme levels, and saw the largest geomagnetic storm since the 2003 Halloween superstorms. DST dipped to -412 on 11 May at 0300 UT. The week began with a relatively benign solar wind environment, indicative of a relatively unremarkable high speed stream that may have included a weak transient passage. With the exception of one active period, the geomagnetic field remained at quiet to unsettled levels until the arrival of a barrage of CMEs described above on 10 May.

Interplanetary shock passage was observed at 10/1639 and followed by a sudden impulse at 1645 of 108 nT at the Boulder magnetometer. Over the remainder of the 10th, the total interplanetary magnetic field strength at L1 increased to 75 nT and Bz remained southward, dipping to -50 nT at times. The solar wind speed jumped from around 450 km/s to 700 km/s with the arrival of the shock, eventually reaching a peak near 1000 km/s on 12/0057. The geomagnetic field responded promptly, and had reached a Kp=7 by 10/1718, Kp=8 by 11/0338, and Kp=9o by 10/2334. The Kp remained at 9o through the 11/00-03 synoptic period, and at 8+ or above for the next 15 hours. A third period of 9o was again observed during the 11/09-12 synoptic period. The Oulu, Finland cosmic ray detector indicated a Forbush decrease of 10% between the 10th and 11th. From 11/1800 to 12/0600 the Kp remained between 7+ and 7- before dropping below minor storm levels through the 12/21 synoptic period. An extremely weak shock was observed at 13/0900 followed by a decrease in density and a jump in temperature. The signature had the hallmarks of a fast stream becoming geoeffective. By 13/1900, the temperature began dropping and the density began rising. This was followed by an increase in geomagnetic activity to moderate (Kp between 6- and 6+) levels.

Space Weather and Propagation Forecast
Prepared by the US Dept. of Commerce, NOAA,
and the Space Weather Prediction Center

Three Day Forecast of Solar and Geomagnetic Activity
(as of 2200Z on 07 Dec 2014)

Solar Forecast:

Solar activity is expected to be low with a chance for M-class flares on days one, two, and three (08 Dec, 09 Dec, 10 Dec).

Geomagnetic Forecast:

The geomagnetic field is expected to be at quiet to minor storm levels on day one (08 Dec), quiet to active levels on day two (09 Dec) and quiet levels on day three (10 Dec).

Forecast of Solar and Geomagnetic Activity
13 May - 08 June 2024

Solar activity is expected to remain at moderate to high levels through the forecast period. Region 3664 will rotate off the visible disk by 14-15 May, and another 10 regions will depart the visible disk between 16 and 23 May. This will lead to a relative lull in activity compared to the past week. However, a couple of regions rotating on will maintain the potential for at least moderate activity. Region 3663 is expected to return on the 23rd and Region 3664 on the 28th of May, with a significant increase in the threat of high activity.

There is a chance for proton events at geosynchronous orbit, particularly with the return of Region 3664. This doesn't preclude the possiblity of an event in the days leading up to the 23rd, but the risk will increase with each day Region 3664 moves across the visible disk.

The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at moderate levels throughout the period.

Geomagnetic field activity is expected to be at minor storm levels to being the period, with a lingering chance of moderate to strong levels through the 14th. A relatively quiet period follows, interupted by coronal hole high speed stream activity between 23 May and 3 June.