Solar Terrestrial Activity Report

Last major update issued on December 14, 2005 at 05:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update December 6, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update December 6, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update December 6, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update December 3, 2005)]

Recent activity

The geomagnetic field was inactive to unsettled on December 13. Solar wind speed ranged between 363 and 474 (all day average 395) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 87.9. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.1)
Three hour interval K indices: 02103112 (planetary), 11213111 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A single C class event was recorded during the day, a C1.7 flare at 21:47 UTC from a source behind the southeast limb.

Region 10830 decayed slowly and quietly and could become spotless before rotating over the northwest limb.
Region 10834 was quiet and stable.
Region 10835 was mostly unchanged and quiet.
New region 10836 reemerged in the southwest quadrant with quite a few spots. This region was first observed with spots on December 10, then became spotless without receiving a region number.

Coronal mass ejections (CMEs)

December 11-13: No obvious partly or fully Earth directed CMEs were observed in incomplete imagery.

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

No obvious coronal holes are currently in or near Earth facing positions.

Processed SOHO/EIT 284 image at 13:06 UTC on December 2. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on December 14-16.

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 fair. Propagation on long distance northeast-southwest paths is very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) with Unión Radio Noticias programming and WLAM Lewiston ME. A station from Colombia and WWNN Pompano Beach FL were noted as well. Most of the usual stations from the east coast of North America were audible at fair signal levels.

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% lower.

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.