Solar Terrestrial Activity Report

Last update issued on January 24, 2003 at 04:05 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 23. Solar wind speed ranged between 532 and 712 km/sec under the influence of a strong coronal stream.

Solar flux measured at 20h UTC on 2.8 GHz was 135.9. The planetary A index was 19 (STAR Ap - based on the mean of three hour interval ap indices: 19.5).
Three hour interval K indices: 54133333 (planetary), 54233323 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 7 spotted regions on the visible disk. Solar flare activity was moderate. A total of 3 C and 2 M class events were recorded. An optically uncorrelated C1.2 event was recorded at 10:15 UTC.

Region 10258 decayed slowly and quietly.
Region 10260 did not change much and has a few small spots.
Region 10263 merged with region S79 and developed quickly. A magnetic delta structure is currently evident in the northern part of the main penumbra. An M class flare is likely. Flare: C4.5 at 02:19 UTC.
Region 10266 developed quickly in the leading spot section as a large amount of positive magnetic flux emerged near the magnetically negative leader spots. Flares: C6.0 at 04:34, M1.0 (with an associated type II radio sweep) at 04:48 and an M2.5/1N long duration event (with an associated type II radio sweep) peaking at 12:44 UTC. [An M1.9 flare was observed in this region at 03:27 UTC on January 24.]
Region 10267 did not change significantly. The hot plage in the trailing spot section cooled.
Region 10268 developed further and has a magnetic delta structure. Minor M class flares are possible.
Region 10269 was quiet and stable.

Coronal mass ejections (CMEs)

January 21-22: No obviously geoeffective CMEs observed.

January 23: A filament stretching from the center of the visible disk and into the southeast quadrant was observed erupting beginning at about 21:24 UTC. So far I haven't been able to detect any obvious CME in LASCO C3 images. If this filament eruption was associated with a CME, the CME will almost certainly 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 huge trans equatorial extension of the southern polar coronal hole was in a geoeffective position on January 16-23. A small trans equatorial coronal hole will likely rotate into a geoeffective position on January 27-28. Another coronal hole in the northern hemisphere will probably be geoeffective on January 30.

Processed SOHO EIT 284 image at 01:06 UTC on January 24. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active until January 27 due to a coronal stream. Quiet to unsettled is expected on January 28-29. 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.