Solar Terrestrial Activity Report

Last major update issued on January 24, 2005 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update November 8, 2004)]
[Archived reports (last update January 19, 2005)]

Recent activity

The geomagnetic field was quiet to active on January 23. Solar wind speed ranged between 565 and 765 km/sec under the influence of a high speed stream from coronal hole CH140.

Solar flux measured at 20h UTC on 2.8 GHz was 95.8. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 16.8).
Three hour interval K indices: 44333432 (planetary), 43332433 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 1 C and 1 M class events was recorded during the day. Region 10720 behind the northwest limbs produced an M1.0 flare at 01:51 and a C4.5 flare at 05:05 UTC.

Spotted regions not numbered by SEC/NOAA:
[S503] This region emerged in the southwest quadrant on January 23. Location at midnight: S22W58.

Coronal mass ejections (CMEs)

January 21-23: No obvious fully or partly Earth directed CMEs were observed.

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 coronal hole (CH141) in the southern hemisphere could rotate to a geoeffective position on January 25-26. A recurrent trans equatorial coronal hole (CH142) will likely rotate to a geoeffective position on January 27-29.

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

Forecast

The geomagnetic field is expected to be quiet to active on January 24 due to a high speed stream from coronal hole CH140. Mostly quiet conditions are likely on January 25-27. On January 28-29 a high speed stream from coronal hole CH141 is likely to cause unsettled to active conditions while effects from coronal hole CH142 could extend these conditions until February 1.

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. When the high speed stream has arrived the color changes to green.
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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along long distance north-south paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: none, a weak unidentified Spanish language station was observed occasionally. On other frequencies only a few stations made it across the Atlantic, WWZN on 1510 had the best signal, but was only heard at times.

Active solar regions (Recent map)

Compare to the previous day's image.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. 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. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.