Solar Terrestrial Activity Report

Last major update issued on December 14, 2007 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 October 4, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update October 3, 2007)]

Recent activity

The geomagnetic field was quiet on December 13. Solar wind speed ranged between 458 and 594 km/s (average speed was 540 km/s, decreasing 45 km/s from the previous day) under the waning influence of a high speed stream from CH303.

Solar flux measured at 20h UTC on 2.8 GHz was 93.8. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.1). Three hour interval K indices: 12111010 (planetary), 12212211 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 3 C class events were recorded during the day.

Region 10978 decayed slightly losing a few spots. The magnetic fields relaxed a little as the distane between the opposite polarity fields increased. Further C class flares are possible. Flares: C4.5/1F at 10:03, C1.0 at 14:06 and C1.7 at 22:00 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S715] This region emerged in the northeast quadrant on December 13. Location at midnight: N12E47.

At N27E48 there is a plage area from a cycle 24 region. Spots could still develop in this area.

Coronal mass ejections (CMEs)

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

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A very large recurrent coronal hole (CH304) in the southern hemisphere will rotate into an Earth facing position on December 14-17.

Processed SOHO/EIT 195 image at 00:12 UTC on December 14. The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor.

Monitoring remarks from a location near N58E06: December 8: Excellent signals were noted on nearly all TA frequencies during my local morning. Stations like 1290 CJBK and 1330 WLOL had huge signals. The Vancouver stations on 1320 and 1470 were occasionally very good.  The best Trans Atlantic propagation sector was 290-320 degrees.

Forecast

The geomagnetic field is expected to be mostly quiet on December 14-16. A high speed stream from CH304 could arrive late on December 16 or on December 17 and cause unsettled to minor storm conditions.

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) Effects from a CME are likely to be observed at 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)

Compare to the previous day's image.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/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/SWPC) 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.