Solar Terrestrial Activity Report

Last major update issued on December 6, 2004 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update December 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update December 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update December 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update November 8, 2004)]
[Archived reports (last update December 1, 2004)]

Recent activity

The geomagnetic field was inactive to active on December 5. Solar wind speed ranged between 288 and 461 km/sec. Two solar wind shocks were observed during the day. SOHO data has a weak shock at 04:14 UTC with an associated abrupt increase in solar wind speed from 300 to 328 km/sec. The source of this shock is likely the faint full halo CME observed on December 1. The second shock was much stronger and occurred at 07:04 UTC. This time wind speed increased from 339 to 443 km/sec. The source is most likely the full halo CME observed early on December 3. The magnetic field associated with this disturbance was very strong. What could have become a major disturbance failed to do that because of extremely poor coupling with the magnetosphere, the IMF was strongly northwards nearly all the time until in the evening when some weak southwards excursions were observed.

Solar flux measured at 20h UTC on 2.8 GHz was 95.9. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.0).
Three hour interval K indices: 01421221 (planetary), 02421221 (Boulder).

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

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

December 4-5: No obviously Earth directed CMEs 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

Recurrent trans equatorial coronal hole CH131 was in a geoeffective position on December 5. CH131 decayed significantly on December 5.

Processed SOHO/EIT 284 image at 01:06 UTC on December 6. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on December 6 and quiet on December 7. Some unsettled and active intervals are possible on December 8-9 due to effects from coronal hole CH131.

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 poor to fair. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela), Radio Cristal del Uruguay and Radio Rafaela (Argentina). Generally speaking signal levels were considerably better than in a long time. Quite a few stations from North America were observed with stations from Newfoundland, New Brunswick and the northeastern USA having the best signals.

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.