Solar Terrestrial Activity Report

Last update December 14, 2002 at 04:00 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 9, 2002)]

Recent activity

The geomagnetic field was quiet to unsettled on December 13. Solar wind speed ranged between 317 and 368 km/sec. A weak coronal stream began to dominate the solar wind after 10h UTC. Solar wind speed has been increasing slowly since then and is approaching 400 km/sec early on Dec.14.

Solar flare activity was low. Solar flux was 166.9, the planetary A index was 7 (STAR Ap - based on the mean of three hour ap indices: 8.5).
Three hour interval K indices: 22122322 (planetary), 11112221 (Boulder). The planetary K indices was exactly the same as on the previous 3 days, extending a pattern which began as early as the 03-06h UTC interval on December 9.

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

At midnight there were 9 spotted regions on the visible disk, 2 of which have not yet been numbered. A total of 13 C class flares were recorded during the day.

Region 10213 decayed and was spotless by late afternoon.
Region 10218 developed slowly and quietly.
Region 10220 decayed slowly. Further low level C class flares are possible. Flares: C3.0 at 01:10, C1.9 at 09:36 and C2.4 at 10:13 UTC.
Region 10223 was mostly unchanged. The region is likely to produce C flares and may be capable of generating a minor M class flare. Flares: C1.5 at 04:46, C8.0 at 13:32 and C6.8 at 17:25 UTC.
Region 10224 decayed and lost a significant amount of penumbra in the leading spot section. The region was much less active than one day earlier. A minor M class flare may still be possible. Flares: C3.4 at 08:36 and C1.6 at 15:32 UTC.
New region 10225 rotated partly into view at the northeast limb on December 12 and was numbered on Dec.13.
New region 10226 emerged quickly in the southeast quadrant and is likely to produce C class flares. If the region continues to develop at the current rate, minor M class flares will soon become possible.
New region 10227 emerged in the northeast quadrant and is developing slowly.

Spotted regions not yet numbered by SEC:
[S55] A new region trailing region 10225 rotated into view at the northeast limb on December 13. Location at midnight: N17E77.
[S56] A new, small region rotated into view at the southeast limb on December 13. Location at midnight: S16E80.

Coronal mass ejections (CMEs)

December 11-13: 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: 30 days ago 26 days ago 25 days ago

A fairly small, decaying, recurrent coronal hole in the southern hemisphere was in a geoeffective position on December 10-11. A trans equatorial, recurrent extension of the southern polar coronal hole will rotate into a geoeffective position on December 15-16.

Processed SOHO EIT 284 image at 19:06 UTC on December 13. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet to unsettled on December 14-16. A weak coronal stream will influence the field on Dec.14, this stream does not appear capable of increasing activity to active levels. A significantly stronger coronal stream is likely to arrive on December 17 and cause unsettled to minor or event major storm conditions. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is fair to good.

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.