Solar Terrestrial Activity Report

Last update December 26, 2002 at 03:45 UTC. Minor update posted at 21:33 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 23, 2002)]

Recent activity

The geomagnetic field was unsettled to active on December 25. Solar wind speed ranged between 409 and 552 km/sec.

Solar flare activity was low. Solar flux was 131.9 (dropping to the lowest level since July 2002), the planetary A index was 14 (STAR Ap - based on the mean of three hour ap indices: 14.5).
Three hour interval K indices: 33334333 (planetary), 32334331 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 5 spotted regions on the visible disk. A total of 9 C class events were recorded during the day.

Region 10224 rotated over the southwest limb. Flare: C4.8 at 05:46 UTC.
Region 10229 decayed and had only a single small spot left by midnight. The region is rotating over the northwest limb.
Region 10230 was mostly unchanged and quiet. Flare: C1.7 at 21:32 UTC.
Region 10231 displayed no major changes and was mostly quiet.
Region 10234 was quiet and stable.
New region 10235 emerged in the northeast quadrant late on Dec.24 and was numbered the day after.

Comment added at 21:33 UTC on December 26: A strong coronal stream began to dominate the solar wind after 15h UTC. Currently the interplanetary magnetic field is strongly southwards and this could result in minor storm conditions during the last hours of today. The background xray flux has dropped all the way to the B3 level and solar flux at 20h UTC was 127.4 (and 123.1 at 18h UTC - the lowest measured solar flux since the first days of August, 2001).

Coronal mass ejections (CMEs)

December 23-24: No obviously geoeffective CMEs observed.

December 25: No LASCO C2 or C3 images available.

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 large and well defined trans equatorial coronal hole was in a geoeffective position on December 24-25.

Processed SOHO EIT 284 image at 19:06 UTC on December 25. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 26. A coronal stream will arrive late on December 26 or early on Dec.27 and cause unsettled to active conditions with the possibility of a few minor storm intervals on Dec.27-28. Quiet to active is expected for December 29 with quiet to unsettled likely on December 30-31. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is 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.