Solar Terrestrial Activity Report

Last major update issued on October 7, 2007 at 03:00 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 October 6. Solar wind speed ranged between 345 and 408 km/s (average speed was 365 km/s, decreasing 78 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 69.0. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0). Three hour interval K indices: 10122212 (planetary), 11222111 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10972 emerged in the southeast quadrant on October 5 and was numbered trhe next day by NOAA/SWPC. The region decayed slightly on October 6 as polarity separation increased.

Coronal mass ejections (CMEs)

October 4-6: No obvious fully or partly Earth directed CMEs were observed in 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 recurrent coronal hole (CH294) in the southern hemisphere could rotate into an Earth facing position on October 8.

Processed STEREO-B 195 image at 21:45 UTC on October 6. 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 fair.

Monitoring remarks from a location near N58E06: October 6: Only a few of the most common signals from North America were audible during the night. The best signals were heard from stations in Colombia, Venezuela, Cuba and Puerto Rico. 1470 kHz had many stations and it was difficult to get proper IDs. Colombian Ondas de Ibagué was one of the better signals. The best Trans Atlantic propagation sector was 255-265 degrees.

Forecast

The geomagnetic field is expected to be generally quiet October 7-16. A few unsettled intervals are possible on October 11-12 due to effects from CH294.

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) 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/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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10972 2007.10.06 5 6 S05W06 0060 CRO formerly region S709
classification was DSO at midnight
Total spot count: 5 6  
SSN: 15 16  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2006.08 79.0 12.9 15.6 (+0.3)
2006.09 77.8 14.4 15.6 (+0.0)
2006.10 74.3 10.4 14.2 (-1.4)
2006.11 86.3 21.5 12.7 (-1.5)
2006.12 84.5 13.6 12.1 (-0.6)
2007.01 83.3 16.9 12.0 (-0.1)
2007.02 77.7 10.6 11.6 (-0.4)
2007.03 72.2 4.8 10.8 (-0.8)
2007.04 72.4 3.7 (10.1 predicted, -0.7)
2007.05 74.4 11.7 (9.0 predicted, -1.1)
2007.06 73.7 12.0 (8.0 predicted, -1.0)
2007.07 71.6 10.0 (7.3 predicted, -0.7)
2007.08 69.1 6.2 (6.8 predicted, -0.5)
2007.09 67.1 2.4 (6.9 predicted, +0.1)
2007.10 67.6 (1) 0.9 (2) (7.6 predicted, +0.7)

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.


[DX-Listeners' Club]