Solar Terrestrial Activity Report

Last update issued on January 21, 2003 at 04:15 UTC. Minor update posted at 17:50 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update January 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2002 (last update October 13, 2002)]
[Archived reports (last update January 20, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on January 20. Solar wind speed ranged between 546 and 738 km/sec under the influence of a strong coronal stream. This coronal stream has its origin in an elongated trans equatorial, huge extension of the southern polar coronal hole and is likely to continue until the end of this week. It should be noted that the easternmost part of this extension is very well defined and could cause the solar wind speed to increase to above 800 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 138.0. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 18.3).
Three hour interval K indices: 54233332 (planetary), 54233332 (Boulder).

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

At midnight there were 8 spotted regions on the visible disk. Solar flare activity was low. A total of 5 C class events were recorded.

Region 10254 decayed slowly and quietly.
Region 10257 decayed and had only a single small spot left at midnight. The region will rotate out of view today.
Region 10258 was quiet and unchanged.
Region 10259 decayed further and is likely to become spotless today.
Region 10260 lost some penumbral area, however, a few additional spots emerged. There is not much separating the positive and negative polarity areas and some mixing is currently observed. Flares: C4.3 at 07:10, a long duration C1.7 event peaking at 19:21 and C1.6 at 23:27 UTC.
Region 10261 decayed and had a couple of small spots left at the end of the day. The region will probably become spotless today.
New region 10264 emerged in the southeast quadrant on January 19 and was numbered the next day. The region decayed and is now spotless.
New region 10265 emerged in the northeast quadrant early on January 20, then decayed and was spotless by early evening.
New region 10266 emerged near the southeast limb on January 19 and was numbered the next day. This region has developed moderately quickly and could produce C flares.
New region 10267 rotated into view at the southeast limb. Flare: C1.5 at 21:46 UTC.

Comment added at 17:50 UTC on January 21: A new region rotating into view at the southeast limb was the source of an M1.9 long duration event peaking at 15:26 UTC. This event was associated with a large CME off of the southeast limb.

Coronal mass ejections (CMEs)

January 18-19: No obviously geoeffective CMEs observed.

January 20: A filament eruption in the northeast quadrant began at approximately 19h UTC with its southwesternmost extension reaching nearly to region 10260. A slowly expanding, bright CME was observed over the northeast limb as early as 19:42 UTC in LASCO C3 images. Early on January 21 this CME became a partial halo CME as it extended south of the equator at the east limb and into the northwest limb. It is still too early to tell if this CME has any geoeffective extensions.

January 21: A type II sweep recorded early in the day was associated with an eruption in region 10260. It remains to be seen if a possibly geoeffective CME was produced.

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 huge trans equatorial extension of the southern polar coronal hole will be in a geoeffective position on January 16-23.

Processed SOHO EIT 284 image at 01:06 UTC on January 21. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm until January 26 due to a coronal stream. 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's 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. All time references are to the UTC day. Comments and suggestions are always welcome.