Solar Terrestrial Activity Report

Last update December 16, 2002 at 04:00 UTC. Minor update posted at 11:03 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update December 2, 2002)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update December 2, 2002)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update December 2, 2002)]
[Historical solar and geomagnetic data charts 1954-2002 (last update October 13, 2002)]
[Archived reports (last update December 16, 2002)]

Recent activity

The geomagnetic field was quiet to unsettled on December 15. Solar wind speed ranged between 437 and 582 km/sec under the influence of a weak coronal stream.

Solar flare activity was low. Solar flux was 203.0, the planetary A index was 9 (STAR Ap - based on the mean of three hour ap indices: 10.3).
Three hour interval K indices: 32223332 (planetary), 22222212 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight there were 9 spotted regions on the visible disk. A total of 12 C class flares were recorded during the day. This includes the following optically uncorrelated flares: C4.3 at 15:53, C5.9 at 18:04 and C3.1 at 22:36 UTC.

Region 10218 decayed quickly and is losing all its trailing spots.
Region 10220 decayed and will soon have lost all trailing spots.
Region 10223 was mostly unchanged and may be capable of producing a minor M class flare.
Region 10224 decayed significantly losing several trailing spots. The region was mostly quiet.
Region 10225 developed slowly and quietly. The region is becoming more complex and currently has mixed polarities. Minor M class flares may be possible. Flares: C2.0 at 08:01 and C2.8 at 10:29 UTC.
Region 10226 developed further and has M class flare potential. There could be a weak magnetic delta in a central penumbra.
Region 10227 developed further as positive magnetic flux emerged at the eastern edge of the main negative polarity area. There is now a weak magnetic delta in this part of the region. Flare: C1.8 at 04:28 UTC.
Region 10228 was quiet and stable.
Region 10229 developed further and has a magnetic delta structure in the eastern part of the large leading penumbra. M class flares are likely, even a major flare is possible. Flares: C2.1 at 00:29, C2.5 at 04:10, C2.0 at 06:28 and C3.1 at 11:36 UTC.

Comment added at 11:03 UTC on December 16: Changes noted during the first half of today: Region 10227 has lost its magnetic delta structure, however, several new spots are visible. Region 10226 is displaying impressive growth and has added many spots. The magnetic delta structure is strengthening and a major flare is becoming possible. Region 10228 has decayed into spotless plage. Region 10218 is decaying quickly and could become spotless before midnight.

Coronal mass ejections (CMEs)

December 13-15: No obviously geoeffective CMEs noted.

Coronal holes

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

A trans equatorial, recurrent extension of the southern polar coronal hole was in a geoeffective position on December 15-16.

Processed SOHO EIT 284 image at 13:06 UTC on December 15. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 16. A strong coronal stream is likely to arrive on December 17 and cause unsettled to major storm conditions late that day and on December 18. Unsettled to active is likely on December 19-20. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is fair.

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)

Composite image based on a SOHO/MDI continuum image and overlaid by a coronal hole image. Region numbering has been included.

Data for all numbered solar regions according to the Solar Region Summary provided by SEC/NOAA. Comments are my own, as is the STAR spot count (spots observed at or just prior to 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 UT observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% 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. Comments and suggestions are always welcome.