Solar Terrestrial Activity Report

Last update issued on October 29, 2003 at 01:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 4, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update October 15, 2003)]
[Archived reports (last update October 22, 2003)]

Recent activity

The geomagnetic field was unsettled to active on October 28. Solar wind speed ranged between 459 and 808 km/sec. A solar wind shock was observed at ACE at 01:30 UTC. This shock was likely related to the arrival of the halo CME observed after an X1 flare in region 10486 on October 26.

Solar flux measured at 20h UTC on 2.8 GHz was 274.4. The planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.6).
Three hour interval K indices: 34443434 (planetary), 24442434 (Boulder).

The background x-ray flux is at the class C3 level. A very strong proton storm is in progress. The above 100 MeV proton flux has so far reached the 180 pfu level, the above 50 MeV flux has peaked near the 1500 pfu level while the above 10 MeV proton flux is still increasing and has gone off scale well above 10000 pfu. The proton levels should increase further just prior to the arrival of the expected solar storm.

At midnight there were 10 spotted regions on the visible disk. Solar flare activity was very high. A total of 5 C, 5 M and 1 X class events was recorded during the day. An M3.2 flare at 15:01 and an M2.0 flare at 16:16 UTC were optically uncorrelated.

Region 10484 decayed fairly quickly losing penumbral area in all parts of the region. A major flare is still possible. Flares: C6.7/1F at 00:59, C7.7/1F at 05:13 UTC.
Region 10486 was mostly unchanged. A thin corridor of negative polarity flux bisects the strong positive polarity area in the central part of the region. Flaring has been observed in the eastern, central and western part of the region. Further major flares are possible. Flares: C7.5 at 01:33, C8.7 at 08:39 UTC. Then an amazing sequence of flares began: First an M1.3 event in the central part of region at 09:56, then an M2.3 flare at 10:09 in the eastern part of region. A long duration major M8.4 event peaked at 10:48 UTC in the eastern part of the region. This event may have triggered a massive X17.2 flare which began at 10:58 UTC and peaked at 11:10 UTC. The X17.2/4B flare was centered in the western part of the region and is the second largest event recorded during solar cycle 23. Strong type II and IV radio sweeps were associated with the X17 flare, as was a very bright, huge and extremely fast CME (speed estimated at well above 2000 km/sec). Additional flares: M3.2 at 14:53 and M2.0 at 16:13 UTC.
Region 10487 was mostly quiet and unchanged.
Region 10488 continued to develop rapidly and is now the second largest region on the visible disk, the leader umbra is extremely large. The region could produce a major flare soon. Flare: C5.3 at 00:45 UTC.
Region 10489 added some small spots while the main spots lost some penumbral area.
Region 10490 was quiet and stable.
Region 10491 developed slowly and quietly.
Region 10492 developed slowly and was quiet.
New region 10493 emerged in the northeast quadrant on October 27 and was numbered by SEC the next day. The region developed slowly on October 28. Region 10488 could soon merge with region 10493.

Spotted regions not numbered by NOAA/SEC:
[S293] A new region emerged in the southeast quadrant on October 28. Location at midnight: S23E45.

Coronal mass ejections (CMEs)

October 28: A full halo and extremely large CME was observed after the X17 flare in region 10486. The CME could reach Earth in less than 24 hours and could create a geomagnetic disturbance equaling or surpassing the great storm in 1989.

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 in the northern hemisphere (CH64) may have been in a geoeffective position on October 25-26. During the previous solar rotation this coronal hole did not cause a geomagnetic disturbance.

Processed SOHO/EIT 284 image at 07:06 UTC on October 28. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to active early on October 29, then reach the extremely severe storm level as a huge solar storm impacts Earth sometime between 06 and 16h UTC. Minor to severe storming is likely on October 30.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is useless. Propagation along north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations none: heard only a very weak signal from Radio Cristal del Uruguay at times. Other frequencies were better, i.e. 930 kHz with Rádio Metropolitana, Fortaleza].

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 analysis, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.