Solar Terrestrial Activity Report

Last update issued on May 29, 2003 at 04:10 UTC. Minor update posted at 13:02 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update May 26, 2003)]

Recent activity

The geomagnetic field was active to major storm on May 28. Solar wind speed ranged between 585 and 716 km/sec under the influence of a high speed stream from coronal hole CH41. This stream weakened during the latter half of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 130.2. The planetary A index was 36 (STAR Ap - based on the mean of three hour interval ap indices: 38.1).
Three hour interval K indices: 65554444 (planetary), 65444443 (Boulder).

The background x-ray flux is at the class B4 level.

A weak proton event is currently in progress. The above 10 MeV proton flux has so far peaked at the 12 pfu level. The source of this event was the X3.9 flare in region S169 early on May 28.

At midnight there were 7 spotted regions on the visible disk. Solar flare activity was high. A total of 15 C and 1 X class events was recorded during the day. A C2.2 event at 14:24 UTC was associated with activity at the southeast limb.

Region 10367 decayed and could become spotless either today or tomorrow.
Region 10368 did not change much, the only development of interest is that the main penumbra is splitting into two penumbrae. Flares: C1.0 at 23:05 UTC. This region was the source of an M1.5/1F flare at 02:18 UTC on May 29. This flare was associated with a weak type IV radio sweep.
Region 10373 was quiet and stable.

Spotted regions not numbered or misnumbered by NOAA/SEC:
[S169] A new region emerged very quickly after noon on May 24 in the southeast quadrant about 11 degrees longitude east of spotless region 10365. The region continued to develop quickly as a compact region on May 25-28 and is currently a complex region with magnetic delta structures along most of the inversion line. The most interesting of these are in the western part of the region where the two largest opposite polarity spots are fairly close to each other. Further X class flaring is likely, and there is even a chance of an X10+ proton flare. Location at midnight: S07W33. Flares: X3.6/2B (associated with strong type II and IV radio sweeps) at 00:27, C7.6 at 04:47, C3.1 at 06:09, C1.9 at 09:45, C1.3 at 12:21, C1.3 at 12:38, C1.3 at 13:55, C1.5 at 15:31, C3.5 at 15:46, C3.5/1F at 17:46, C2.0 at 18:08, C4.4 at 18:44, C1.9 at 19:39 and C1.5 at 22:06 UTC. This region generated an X1.1/2B flare at 01:05 UTC on May 29 as well.
[S171] A new region emerged in the southeast quadrant on May 28 due north of region 10368. Location at midnight: S23E02.
[S172] A new region emerged on May 28 in the southwest quadrant in the middle of coronal hole CH42. Location at midnight: S17E21.
[S173] A new region emerged on May 28 in the northeast quadrant west of region 10373. Location at midnight: N05E44.

Comment added at 13:02 UTC on May 29: A solar wind shock was observed at SOHO at noon with a sudden increase in solar wind speed from 570 to 730 km/sec. This was likely related to the arrival of the full halo CME observed 52 hours earlier in LASCO images after a long duration M1.6 event in region S169. The next shock could arrive within hours.

The above 10 MeV proton event is currently at the 30 pfu level and increasing slowly.

Coronal mass ejections (CMEs)

May 27: A full halo CME was observed in LASCO C3 images starting at 07:42 UTC. This was likely associated with a long duration M1.6 event (peaked at 06:26 UTC) in region S169. The CME could reach Earth on May 29 but may be overtaken by another (larger and faster) CME.
Another full halo CME was first observed in a LASCO C2 image at 23:50 UTC. This CME was associated with an X1.3 flare in region S169 and will likely reach Earth during the latter half of May 29.

May 28: The X3.9 flare in region S169 early in the day was associated with a fairly large full halo CME first observed in LASCO C2 at 00:50 UTC. This CME will likely arrive together with the CME observed one hour earlier and could cause a complex geomagnetic disturbance. late on May 29 and on May 30.

May 29: Another full halo CME was observed early in the day after an X1.1 flare in region S169. This CME will probably arrive at Earth during the latter half of May 30.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole (CH41) in the southern hemisphere was in a geoeffective position on May 24-25. A large recurrent coronal hole (CH42) in the southern hemisphere will rotate into a geoeffective position on May 29-June 2.

Processed SOHO EIT 284 image at 19:06 UTC on May 28. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to severe storm on May 29-31 due to several CME impacts. A high speed stream from coronal hole CH42 will likely arrive on June 1 and cause unsettled to minor storm conditions lasting until June 6.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely stay very poor until at least June 8. Propagation along north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]

Coronal holes (1)	Coronal mass ejections (2)	M and X class flares (3)

1) Effects from a coronal hole could reach Earth within the next 5 days.
2) Material from a CME is likely to impact Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions (Recent map)

Compare to the previous day's image.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SEC or where SEC has observed no spots.

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.