Last major update issued on December 18, 2004 at 05:30 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 14, 2004)]
The geomagnetic field was quiet to active on December 17. Solar wind speed ranged between 538 and 661 km/sec under the influence of a high speed stream from coronal hole CH133.
Solar flux measured at 20h UTC on 2.8 GHz was 89.9. The planetary A
index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 15.0).
Three hour interval K indices: 34332323 (planetary), 35432322 (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.Region 10710 was quiet and stable.
Spotted active regions not numbered by NOAA/SEC:
[S489] This region emerged early in the day just to the east of region 10710. Unfortunately SEC/USAF did not manage to separate this emerging bipolar region from the stable bipolar region 10710.
December 15-17: No obviously Earth directed CMEs observed. A full halo CME was observed in LASCO C3 images after 19h UTC on December 15. Its source was likely a few days behind the northwest limb.
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
An extension (CH133) of the northern polar coronal hole was in a geoeffective position on December 13-14. A recurrent coronal hole (CH134) in the southern hemisphere will likely rotate into a geoeffective position on December 18.
Processed SOHO/EIT 284 image at 18:03 UTC on December 11. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on December 18 under the influence of a coronal hole flow and quiet on December 19-20. Another and weaker coronal hole flow could arrive on December 21 or 22 and cause some unsettled and active intervals.
|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.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor (approaching poor to fair). Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and WLAM Lewiston ME. Several stations from the easternmost parts of North America could be heard on other frequencies with the best signals above 1400 kHz.
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.
|Active region||Date numbered||SEC
|Location at midnight||Area||Classification||Comment|
classification was DAO
see region S489
|Total spot count:||10||12|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2004.06||97.4||43.2||(42.2 predicted, -1.7)|
|2004.07||119.1||51.0||(40.6 predicted, -1.6)|
|2004.08||109.6||40.9||(39.0 predicted, -1.6)|
|2004.09||103.1||27.7||(37.1 predicted, -1.9)|
|2004.10||105.9||48.4||(34.9 predicted, -2.2)|
|2004.11||113.2||43.7||(33.0 predicted, -1.9)|
|2004.12||92.6 (1)||20.1 (2)||(30.7 predicted, -2.3)|
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.