Solar Terrestrial Activity Report

Last update December 23, 2002 at 03:00 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 16, 2002)]

Recent activity

The geomagnetic field was quiet to active on December 22. Solar wind speed ranged between 370 and 547 km/sec. A solar wind shock was observed at approximately 0920 UTC at SOHO. Solar wind speed increased from 370 to 520 km/sec over the first 20 minutes after the shock. The interplanetary magnetic field was mostly northwards during the day and this resulted in only a weak disturbance. Since just before midnight the IMF has swung slowly southwards and is moderately to strongly southwards early on Dec.23.

Solar flare activity was moderate. Solar flux was 172.0, the planetary A index was 12 (STAR Ap - based on the mean of three hour ap indices: 12.3).
Three hour interval K indices: 22233342 (planetary), 22223342 (Boulder).

The background x-ray flux is at the class B8 level.

At midnight there were 7 spotted regions on the visible disk, 1 of which has not yet been numbered. A total of 8 C and 1 M class flares were recorded during the day.

Region 10223 decayed further. At the current rate of decay this region will become spotless before rotating over the northwest limb on Dec.25. Flare: M1.1/2F long duration event peaking at 02:52 UTC.
Region 10224 was the only region on the disk displaying significant development. The magnetic delta structure in the trailing spots strengthened and the region should be capable of producing a minor M class flare.
Region 10226 decayed quickly in all parts of the region and was quiet.
Region 10229 decayed quickly and could actually become spotless before rotating over the northwest limb on Dec.26.
Region 10230 decayed slowly and quietly. A minor M class flare is still possible.
Region 10231 did not change much and was quiet.
Region 10232 decayed and was spotless by late afternoon.

Spotted regions not yet numbered:
[S59] A new region emerged in the northeast quadrant. Location at midnight: N10E55.

Coronal mass ejections (CMEs)

December 20: No obviously geoeffective CMEs observed.

December 21: A large filament eruption at high latitudes in the northern hemisphere early in the day was associated with a partial halo CME observed off of the northeast and northwest limbs as well as the north pole. This CME is probably not geoeffective.

December 22: A CME was observed off of the northwest limb early in the day after an M1.1 flare and an associated filament eruption in region 10223. The CME does not appear to be geoeffective.

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 trans equatorial coronal hole will likely reach a geoeffective position at the central meridian on December 24-25.

Processed SOHO EIT 284 image at 19:06 UTC on December 22. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on December 23 and quiet to unsettled on December 24-25. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is poor to very poor.

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. Compare to the previous day image.

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 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 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.